1 1/2 cups all-purpose flour
3/4 cup (1 1/2 sticks) unsalted butter, cut into quarters
1/4 cup sugar
Pinch of salt
1 large egg, lightly beaten with 1 tablespoon ice water
4 large eggs, separated
2/3 cup sugar
12 ounces Ricotta cheese (drained if watery)
2 tablespoons grated lemon rind (from about 2 large lemons)
3 tablespoons lemon juice
4 teaspoons potato starch
1 teaspoon vanilla extract