Filling: Bring first four ingredients to boil in a heavy large saucepan, stirring to dissolve sugar. Whisk egg in medium bowl to blend. Gradually whisk in hot butter mixture. Return mixture to saucepan and stir over medium heat until mixture thickens and leaves path on the back of spoon when finger is drawn across, about 2 minutes. Pour into bowl, cover and chill over night.
Crust: Finely grind almonds in food processor. Transfer to bowl and mix in flour, 1/4 c sugar and salt. Blend butter, 1 egg, milk, lemon peel, and vanilla in processor until combined. Add dry ingredients and blend in using on/off turns until dough begins to come together. Turn dough onto lightly floured surface and knead until just smooth. Divide dough into 2 unequal pieces that are 1/3 and 2/3 of entire amount. Flatten each piece into disk. Wrap in plastic and refrigerate at least 30 minutes.
Preheat oven to 375°. Roll out larger dough piece between sheets of waxed paper to 12" round. Peel off top sheet of paper. Press dough into bottom and up sides of pan, forming a 1/2" high rim of pastry above pan. Crimp edge. Spoon cold filling into tart shell. Roll out smaller dough piece between sheets of waxed paper into 9" round. Place atop filling in tart. Press dough top and sides together to seal. Fold crimped edge in. Press with fork tines to form decorative design.
Bake tart until top is brown, about 35 minutes. Transfer to rack and let stand 5 minutes. Brush top of tart with egg white; sprinkle with sugar. Bake 10 minutes more. Transfer tart to rack and cool completely. Remove tart pan sides. Transfer tart to platter. Cut into wedges. Top with cream, berries and mint.