♪♪ ♪♪ ♪♪ ♪♪ ♪♪ -Today on "America's Test Kitchen," Keith and Julia reveal the secrets to making perfect swordfish steaks, Jack challenges Bridget to a taste-test of capers, Lisa reviews indoor gardens, and Becky makes Bridget the best summer tomato gratin.

It's all coming up right here on "America's Test Kitchen."

♪♪ -Swordfish, also known as broadbill, is one of the fastest and most powerful fish in the ocean.

The often travel alone, and they can be quite elusive, which means they're hard to catch, and therefore quite expensive.

So when you finally bring a great piece of swordfish home to cook, you don't want to mess it up.

So Keith's here to show us how to cook it the right way.

-You're right.

Swordfish can be a little expensive, but there are a lot of positive traits.

In fact, a lot of traits that are like steak.

It's firm, so it's really easy to flip and get it in and out of the pan.

There's no fish breaking on you.

They also have a dense, meaty texture, so that it really appeals to carnivores.

But, like fish, it really is easy to overcook.

It can become dry, or it can become mushy.

So before I cook our fish, we've going to make a quick relish to serve with the fish.

So it's a quick take on an Italian agrodolce.

So I have 3 tablespoons of extra virgin olive oil.

I'm going to add 3 tablespoons of minced parsley to that.

I'm going to add two tablespoons of capers that have been rinsed and minced.

We're going to add one garlic clove that has been minced.

2 tablespoons of currants that have been chopped fine, and we have 2 tablespoons of lemon juice.

We're going to add 1 teaspoon of lemon zest.

I'm going to stir this together.

-Mmm.

-Okay, so that is all mixed together, and this needs to sit for about 20 minutes for those flavors to meld.

But now we can use that time to prep our swordfish.

So, we're working with 2 pounds of swordfish steaks that are about 3/4 to an inch thick.

We're going to be cooking four steaks of swordfish.

We want about 7 to 9 ounces each.

Typically, you find swordfish like this, already cut into pieces at your fish market, but sometimes you'll also find it in large steaks like this.

So there's some prep work that you have to do if you do find it like this.

The first thing we want to do is we want to take out this line of blood right here, the myoglobin.

Some people like that flavor.

-Mm-hmm.

-It has a kind of mineral-y flavor.

It has that kind of strong flavor for some people, so what you want to do is you want to just kind of cut on either side of that.

And we also want to remove the skin from this, too.

So you want to just stand it up.

You just put your knife like that.

-I love buying fish with the skin on because the skin can tell you a lot about how fresh the fish is.

You want a skin that's not dried out and is quite pliable, but you definitely want to cut it off before cooking.

-Okay, so our steaks are ready.

We just have to let our sauce sit for a little bit longer, and we'll come back and cook our steaks.

-Sounds good.

-Okay, so our sauce has had time to meld, and now it's time to cook our swordfish.

I have a 12-inch skillet here with 2 teaspoons of vegetable oil, so I'm going to heat that over medium/high heat.

-Now, we're not huge fans of using non-stick skillets all the time here in the test kitchen, but for cooking fish, it's crucial so that the fish doesn't stick.

-That's right.

So, before we cook our swordfish, I just want to take a paper towel and make sure that the surface of the fish is nice and dry on both sides.

Now, I have 1 1/2 teaspoons of kosher salt here.

I'm going to season both sides of the swordfish.

We like kosher salt here.

It sticks to the surface nicely, and you can also see where it's going, too.

Okay, so our fish is salted, and now it's going to come time to sear.

Now, we tried a couple different methods for searing the swordfish.

The first one we tried was reverse sear, which is really good for steaks.

You start slow, you bring it up to temperature, and you do a quick sear right before you serve it.

We liked that, but we found with swordfish, it actually turned it mushy.

So, we went to another steak method, which is flipping it often in the skillet.

So, when you flip it often, instead of just introducing heat to one side and then flipping it halfway through, you're flipping it every two minutes.

When you turn that swordfish over, the top still retains some heat, so it actually cooks down from the top and the bottom.

So we can reduce the cooking time by about 30% but still get nice browning.

Okay, so our oil is shimmering.

You can see it kind of skitter across the surface there, and we can put our swordfish in.

We want to cook these swordfish steaks for 7 to 11 minutes until they're nice and golden-brown.

Okay, so we're going to let this go for two minutes and then flip it over.

I have my timer right here, and I'm going to press "start."

If you're ever searing swordfish in a non-stick skillet, or any fish or any steak, for that matter, sometimes you'll find that the oil will pool to one side.

-Mm-hmm.

-So, what I'll do is I'll go in and kind of pick up the fish and kind of make sure that that oil gets back underneath the fish.

And also just spin everything around, kind of clockwise.

-Mm-hmm.

Just to make sure that oil is evenly distributed.

-So it's been two minutes, and we're going to do our first flip.

Now, I'm using tongs here.

-I was going to say something.

-Well, that's the beauty of swordfish right?

You can use tongs to flip it over.

Sometimes it's nice to have a spatula to kind of give you an assist... -Mm-hmm.

-...but you should be able to get your tongs right underneath there.

Flip it over.

So that's our first side.

In two minutes, you can start to see we're getting some browning.

It will get more brown when we go on the other side, but now another two minutes on this side.

Been four minutes.

I'm going to flip this over again.

-Let me guess.

Two more minutes.

-Two minutes.

Okay, I'm just going to flip this over, then another two minutes.

These are looking great, and we should probably start temping now.

So, our ideal serving temperature for the swordfish is 140 degrees, but since this pan is fairly hot, we want to under-cook it slightly and let it carry over.

So, we're going to take it out of the pan at 130 degrees.

Okay, 130 degrees.

That's perfect.

We want to get that out of our pan.

You can hear my timer going off here.

Okay, so those have to rest 10 minutes, and then we can go and eat them.

-Okay.

So Keith just said that flipping the fish as it cooks every two minutes will save time, and actually, we found out it only saves two or three minutes, which doesn't sound like a lot.

But that can add up and will have a huge effect on the texture of the swordfish.

You see, fish contains enzymes called cathepsins, which are most active at warmer temperatures.

These enzymes break down long protein molecules into shorter pieces, and as the protein breaks down, the swordfish becomes mushy.

Therefore, the cooking speed matters, especially with thicker pieces of fish with long cooking times, such as swordfish.

The more time the fish spends at cooking temperatures, the longer the enzymes have to do their dirty work, turning the swordfish from meaty to mushy.

And that's why flipping the swordfish steaks every two minutes to help them cook faster is key.

-Okay, so it's been 10 minutes, and now it's time to eat.

-The fish is beautiful.

-Isn't it beautiful?

-Mm-hmm.

Mmm.

-Some relish for you, some relish for me.

-Thank you for the extra relish.

-Okay, let's dig in.

-Oh, this is beautiful.

Mmm.

Perfectly cooked.

A little bit of browning on the outside, but nice and moist on the inside.

-Also, that texture's so great.

It really is meaty.

It's hefty.

It's not like a flaky cod fillet.

It just has so much heft to it.

-And this relish is delicious.

It would make anything taste good.

It's that balance of the acidity of the lemon and that lemon zest.

A little bit of sweetness, and then lots of parsley.

So, at the end of the day, it tastes savory and not sweet, but I appreciate that little bit of sweetness in the middle.

Mmm, thank you, Keith.

-You're welcome.

-So, there you have it.

If you want to make this fabulous recipe, start with 2 pounds of swordfish.

Trim away the skin and some of the red blood line and season with salt.

Using a non-stick skillet over medium-high heat, cook the fish, flipping it every two minutes, until it's golden-brown and registers 130 degrees.

Let the fish rest for 10 minutes, then serve with a delicious caper-currant relish.

So from "America's Test Kitchen" to your kitchen, a great new recipe for pan-seared swordfish steaks.

Killer.

♪♪ -Capers are like the perfect pickle in petite parcels.

I love them, and I love Jack.

And he's here to tell us about supermarket capers and why we should buy the top winner.

-Well, that's a very nice introduction.

I love that you got through that, you know?

That was not easy.

-Whew!

-Well, hopefully this will be just as easy for you.

-I got to taste them.

-You have to taste them.

So, as you said, these are pickles.

-Mmm.

-Capers are the little flower buds from a Mediterranean shrub that are either salted or put in brine.

Now, these are all the kind that are in the brine.

Simply take them out of the jar.

You put them into your chicken piccata, your pasta puttanesca.

Those dishes require the saltiness, the brininess, the slight floral crunch of a perfect caper.

You will see some textural differences.

Some of them are a little soft, maybe even a little mushy.

-Mm-hmm.

-So, of course we've never eaten unpickled capers.

-I surely have not.

-Yes, they are not very delicious.

So, to turn them into pickles, they are brined, generally for about 25 days.

After the capers have been brined, they're put in jars with water, salt, and vinegar or another preservative.

Anything that you're noticing?

I mean, I really feel like I should have made piccata or puttanesca for you, as opposed to just bowls of caper.

-I got to say, I'm enjoying myself.

Oh, I'm supposed to taste these, right?

Not just eat them.

-Yeah, well, you can just eat them.

These are all small, so one of the things that we have learned over the years in the test kitchen is we prefer the nonpareil, which is the designation for a small size.

The larger ones can be almost just too salty or too briny if you get a whole one, and we'd rather not have to chop them up... -Right.

-...in a lot of recipes, and just be able to use them whole.

-I've got to say, they're all pretty good.

They really range in degrees of puckery-ness.

There's a little bit of a texture issue, too.

Some of them are softer than others.

I think I'm ready to pick my winner, though.

-Okay.

-Do you want to know?

-Yeah.

-I think I like this one.

I thought it was grassy.

-Okay.

-It had a really nice texture.

I would say this is my close second.

Pretty puckery, which I kinda liked.

And this one would be the one I like the least.

The texture of it was a little too soft for me.

-So, we'll see.

All the brands that we tasted, the panel ended up recommending.

But you know what?

You're perfect.

-Practically perfect in every way.

-Pretty much.

You've got the winner.

This is the Reese.

The tasting panel liked it.

Flavor, texture, just the perfect caper.

-It really is, yep.

Alright, let's check out my second place here.

-That's Crosse & Blackwell.

Again, I said all the brands are recommended.

It's a fine caper.

-It is a fine caper.

And here we go.

-Mediterranean Organic.

This one was actually a little higher up in the ratings than I think you gave it, because it was at the bottom of your rankings, but let's just focus on what you got perfect, which is you picked the winner.

-Yes, I picked the winner.

And that's the caper caper.

There's no mystery.

You can't lose with any of the capers, but if you want to buy the winner, it's the Reese nonpareil capers and it's $4 for a 3 1/2-ounce jar.

Thanks, Jack.

♪♪ -Fresh herbs add a jolt of flavor to your cooking, and if you grow them yourself, they're as fresh as possible.

Indoor gardens promise to make it easy, even if you lack outdoor space or sunlight.

We tested these four models, all priced around $200.

Each has full-spectrum grow lights that mimic daylight and more or less self-watering systems.

Three were smart gardens, and they had apps that cycled the lights on and off and sent alerts to help you take care of the plants with plant food and water, and we bought two of each of these gardens.

We put one set in a windowless room and the other set in a room with windows but away from direct sunlight.

Here's what we learned.

Natural light didn't matter.

Both sets performed about the same, but these two gardens were just not good.

This one by Eden -- it might look healthy, but trust me, it is a huge pain to set this thing up and the arch of lights is too low.

These two did better.

The Miracle Grow aero-garden grew like wildfire.

Only problem is the plants overgrow, and the garden sends you non-stop notifications for more water, no matter how often you fill it, 'cause this tank is just too small.

And that leaves our winner.

It's called the Smart Garden Nine by Click and Grow.

This thing, dead simple, even for people who lack green thumbs, like me.

Plants grew within a week or two.

You can choose from dozens of plants and herbs and flowers.

The app is simple, but you barely need it.

The pods come pr-seeded with built in fertilizer, and you never have to mess around with little droppers of plant food, like the others.

The lights cycle on their own, and this arch leaves plenty of room for the plants to grow tall.

It's easy to water, and this big enclosed tank holds plenty of water for weeks.

You just pour it in till the bobber rises up, and that's all you have to do except enjoy the warm glowing light and all the fresh herbs you grew all by yourself.

Easy peezy.

♪♪ -It's the middle of summer, and those tomatoes -- they are at peak perfection.

So what do you do?

You pick them, slice them, and maybe season them with salt and pepper, or perhaps you just dress them and add them to a salad.

But do you cook them?

No, you don't, because you know that that is equivalent of culinary blasphemy.

Or is it?

-Hi, Bridget.

-Becky's here, and she's going to tell us about a great dish that might just convince us otherwise.

-I hear you're a little bit skeptical.

-Yeah, just a tad.

-Just a little bit, but this is actually a really nice way to use up tomatoes when they're plentiful, when you have those great tomatoes.

And cooking actually intensifies the nice, fresh tomato flavor.

-Alright, we shall see.

-Alright.

[ Laughs ] So, a tomato gratin -- it combines fresh tomatoes.

There's bread to soak up all those delicious juices from the tomatoes that they release during cooking, and then a little bit of Parmesan cheese on top, which will add some nice flavor and texture.

-Nice.

-So, before we get to the tomatoes, we're actually going to start with our bread topping.

-Okay.

-We're going to make some nice croutons to go on top.

Now, this is a really nice artisan-style baguette.

We tried making this recipe with sandwich bread.

We also tried sort of squishy supermarket baguette.

Both of those got really mushy during cooking.

That's a really common problem with these, so you really want to take the time and find a nice baguette that has some chew to it.

This is 6 ounces of baguette cut into 3/4 inch cubes here... -Okay.

-...and I have a 1/4 cup of extra virgin olive oil that we're going to heat over a medium-low heat.

We're using a good amount of oil here.

The tomatoes themselves are lean.

They're completely fat-free, so this will add some nice richness.

Okay, so our oil is shimmering.

Let's go ahead and add our bread to the pan.

So we want to stir and get these nice and coated in the oil, and we're going to cook these for about five minutes until they get all nice and brown and toasty.

-And Becky mentioned earlier why it's important to use an artisan baguette.

Take the time to find that instead of that really low-quality supermarket baguette.

We've done a little test to show you.

These are two different types of baguette.

This one here is straight from the supermarket.

It kind of looks like sandwich bread.

Now, they both soaked up water very well, but look what happens when I just start to work with this.

Yeah, it just mushes, falls apart, and it really expels all of those juices.

I don't know what that is, but it's not good.

Now, this is the artisan loaf here, and you can see it also expels some juices but it's retaining its shape here.

So imagine if this was in our tomato gratin, these would still be nice, intact pieces of bread.

This would be -- well, like tapioca pudding.

Not good.

-Alright, it's been about five minutes.

We can actually hear that this bread is ready, right?

-[ Laughs ] Yes, very, very crisp.

-Yes, that's how we want it.

Alright, so we'll kill the heat here and put these back in the bowl.

So now we'll get to the tomatoes.

So, we need 3 pounds of tomatoes, and you really want to use the best, ripest, and seasoned tomatoes you can find for this recipe.

-Okay.

-It will work with supermarket vine-ripened tomatoes, but the gratin just won't be quite as flavorful.

-Gotcha.

-You don't want to use plum tomatoes.

Those are actually relatively dry, and they won't have enough juices.

So, the gratin will bake up sort of dry.

We'll just cut our last tomato here.

We want to take out the core, and then we're going to cut it the same size as the bread, about 3/4-inch pieces.

Okay, so our tomatoes are ready to go there.

-Beautiful.

-And now we're going back to our skillet.

-Okay.

-So, we'll get some low heat, and 2 more tablespoons of extra virgin olive oil.

-Okay.

We don't need to wipe out the pan or anything?

-Nope, everything is going back in.

It's all going to the same place.

We just want to get that a little bit heated up.

-And that pan was pretty hot, so that shouldn't take very long.

-Right.

So now I'll add 3 cloves of thinly sliced garlic.

-Okay.

I like where this is going.

-Oh, yeah, garlic and tomatoes.

-Mmm.

-As soon as it hits the pan, you start to get that really nice smell.

We're going to cook this for 30 to 60 seconds.

We just want the outer edges of the garlic to start to get golden here.

-I like that you use sliced garlic instead of minced garlic, so you're going to get a more subtle garlic flavor.

-Yeah, I was hoping you'd pick up on that.

-Yeah.

-That's smelling amazing.

I think that is our signal that we can add our tomatoes.

So, in goes our tomatoes.

That's 3 pounds.

That's a lot.

Now, I have 2 teaspoons of sugar, and that's going to just bring out the natural sweetness that the tomatoes have.

A then a teaspoon each of salt and pepper.

And now we'll just increase the heat to medium-high.

We want to cook this for 8 to 10 minutes until the tomatoes release enough juices so that they're mostly submerged.

-Okay.

-We're going to really concentrate those juices and evaporate a few of them, too, so the gratin isn't too watery.

-I see, okay.

And how long?

-8 to 10 minutes.

-Alright.

Ahh, heavenly smell.

-Taking a nice, deep inhale.

-Amazing, amazing.

-So, you can see, quite a bit of those juices have come out.

It's starting to smell, like you said, really good in here.

The tomatoes are all cooked.

I'm going to turn the heat off.

So now we're going to add some of our bread.

I took out 3 cups of the bread, and I'm leaving one cup behind, just for now.

-Okay.

-I want to mix in most of the bread.

It's going to create a really nice, soft, almost bread-pudding-like kind of texture when it soaks up some of those juices.

So, I'm going to stir those in.

So you want to get all this bread completely coated... -Ahh.

-...in those juices.

Okay, so now I'm pressing down with my spatula.

I really want to get all those pieces underneath so they can soak up those delicious juices.

-It is like a bread pudding.

-It is.

Okay, and then I have the one cup left over, and I'm just going to scatter these over the top.

Now, these will bake up nice and crunchy, so we have some nice contrast on top.

-The gratin part of gratin.

-Ooh, mais oui!

And now I just want to press these down just a tiny bit, just so they don't go anywhere, just right on top.

Okay, and now our final touch is 3/4 cup of Parmesan cheese that's going to be salty and nutty.

It's going to brown.

I mean, yeah.

-A thing of beauty.

-Yes.

Okay, so we're going to bake this in a 350-degree oven for 40 to 45 minutes.

After 30 minutes, I'm going to go in with a spatula and loosen it around the edges, just to loosen any crust and let any juices come up.

This is not going to break down and turn into a sauce.

We're not going to stir it.

It's relatively low heat, so we're still going to have some nice, intact pieces of tomato.

-Okay, no tomato sauce.

-No, I guarantee.

-Okay, alright.

[ Sniffles ] Ahh, oh, wow.

-Ooh, that smells good.

-Bubbling and brown.

-Yes.

Mmm-mmm-mmm.

Alright, so that was 45 minutes.

It smells amazing.

Now, you'll see it's a little bit jiggly right now.

See when I shake it?

-Oh, yeah.

-So, we're going to let this cool for 15 minutes, and it will set up a little bit.

So it's important to let it cool.

So, I'm going to leave this towel on the handle here, so we remember not to touch it.

We don't burn ourselves.

Okay, so it's been about 15 minutes, and you can see the jiggle has mostly gone.

So, before we dive in, I'm going to prepare just a little bit of fresh basil.

We need about 2 tablespoons here, and it's nice to chop basil at the last minute... -Yes.

-...so it stays super fresh.

It will turn sort of dark and discolor otherwise.

-That smells incredible.

-Oh, my gosh, I know.

One of my favorite smells.

So, I'm just rolling the leaves up a little bit here.

It makes them a little bit easier to chop, and we go through them in one direction.

This is a pretty rustic dish.

It doesn't have to be fancy at all.

And that looks close to 2 tablespoons.

Just give that a nice sprinkle over the top.

-Ooh, wow.

As soon as they hit that hot tomato and hot cheese on top, you can smell that basil.

That's gorgeous.

-I know.

Alright.

-That's it, right?

-That's it.

-Okay, no more waiting.

-Let's dive in.

-Ah, yes.

And you serve it like a bread pudding, too.

Nice and scoopy.

-That's right.

There you go.

-Alright.

So you do see pieces of tomato in there, and I wasn't sure if you were being completely truthful with me.

-You didn't trust me?

-Well, I always trust you, but I know summer tomatoes.

They just want to fall apart.

-Yeah.

-But really, I think the bread in there absorbed enough of that juice so the tomatoes weren't actually stewing in their own juices for the entire time.

-Exactly.

-Alright.

Really, really -- I mean, you're right.

The tomatoes concentrated down.

A little bit of sweetness was released, very seasoned.

I love these bits of bread.

They're kind of like little dumplings.

-Yes, that's it.

Soaked full of tomato juice.

They kind of expand with all the juices.

-You did everything to bring out the best of the tomatoes.

You treated them very simply, just chopped them, and you had that oil and the bread, let them stew in that, but you didn't add a lot to the pan.

You weren't trying to mask that flavor of tomato.

This really is incredibly elegant.

-Yes, well, for an elegant lady... -Right.

-...an elegant dish.

-I love that last-minute flourish of basil.

It's perfect.

-Mm-hmm.

-I couldn't have asked for anything more.

Except maybe more.

-[ Laughs ] There's plenty.

-Well, there you go.

This beautiful summer tomato gratin starts with bread cubes toasted in a skillet.

Cook garlic in oil, then add tomatoes, sugar, and salt and cook them until the tomatoes are submerged in their juices.

-Off heat, stir in 3 cups of the bread cubes and arrange the remaining bread on top.

Sprinkle with Parmesan and bake until bubbling.

Cool, top with basil, and serve.

-So there you have it from "America's Test Kitchen" to your kitchen, a symphony of summer.

It's the best summer tomato gratin, and you can get this recipe and all the recipes from this season, including tastings, testings, and select episodes, on our website.

That's AmericasTestKitchen.com.

This would be perfect with grilled anything.

-Oh, I know, right?

Or even just by itself.

-Mm-hmm.

-Let us help you with dinner tonight.

Visit our website anytime for free access to the newest season's recipes, taste tests, and equipment ratings or to watch current-season episodes.

Log on to AmericasTestKitchen.com/tv.

♪♪ ♪♪ ♪♪ ♪♪ ♪♪ ♪♪