Trim the ends from the lemons, then quarter them lengthwise. Slice them paper-thin and remove any seeds. Toss the lemon slices with sugar and vanilla. Cover and refrigerate for 24 to 48 hours.

Pulse flour, sugar, and salt in a food processor. Add frozen butter and process until the largest bits are pea-sized. Transfer to a bowl.

Stir vodka, vinegar, and 4 tablespoons of ice water together. Drizzle over the flour mixture and stir until shaggy.

Turn dough onto a surface, knead in an additional tablespoon of ice water if needed. Shape into a block about 1 inch thick, cut into 4 pieces, stack and flatten repeatedly to create layers.

Divide into two disks, wrap, and chill for at least 3 hours.

Preheat oven to 450°F. Whisk eggs, cornstarch, and salt into the lemon mixture.

Roll one dough disk into a 12-inch round, fit into a pie plate. Pour in the filling.

Roll out the second dough disk, place over the filling, tuck it under, and crimp the edges. Brush with egg wash and cut slits in the top.

Set pie on a heated baking sheet, bake for 15 minutes, then lower heat to 375°F and bake for about 1 hour 15 minutes until golden and set.

Beat heavy cream and confectioners' sugar until soft peaks form. Chill until serving.

Let pie cool completely before slicing. Serve at room temperature with whipped cream.