8 slices prosciutto (about 4 ounces total) halved lengthwise and thinly sliced crosswise, about 1 cup
1 tablespoon finely grated lemon zest
1 tablespoon fresh lemon juice
1/2 cup finely grated Parmesan cheese plus more for serving (optional)
In a large pot of boiling salted water, cook pasta until al dente, according to package instructions. Reserve 1 cup pasta water; drain pasta and return to pot.
Meanwhile, make sauce: In a large skillet, melt butter over medium-low heat; add shallot and cook until softened, about 5 minutes. Add cream, peas, and prosciutto; bring to a gentle simmer over medium heat. Simmer until peas are heated through, 3 to 4 minutes.
Stir in lemon zest and juice. Add enough reserved pasta water to thin sauce as desired.
Pour sauce over pasta; add Parmesan, and season generously with salt and pepper. Serve immediately; top with additional Parmesan, if desired.