1. On a lightly floured work surface, roll 1 piece of pate brisee into a 15-inch round. With a dry pastry brush, sweep off the excess flour; fit dough into a 9-inch pie plate, pressing it into the edges. Trim to a 1-inch overhang all around. Crimp edge as desired. Cover with plastic wrap; chill pie shell until firm, about 30 minutes. Repeat process for rolling out dough. Using a 4-inch grape leaf cookie cutter, cut out 4 leaves from dough. Transfer to a baking sheet, cover with plastic wrap, and refrigerate overnight.

2. Remove skins from grapes by pinching the ends of each grape, reserving both the pulp and skins separately, discarding any accumulated liquid.

3. Place pulp in a saucepan; bring to a boil. Cook until the seeds separate from the pulp and the pulp breaks down, about 6 minutes. Strain mixture through a sieve into the bowl with the reserved skins; discard solids. Let cool to room temperature before placing in the refrigerator for 2 hours.

4. Preheat oven to 450 degrees. Remove grape mixture from refrigerator. Stir in sugar and cornstarch. Pour into prepared pie shell. Beat egg with 1 tablespoon water. Brush edge of pie shell with egg mixture, reserving any remaining mixture. Transfer pie to oven; bake 10 minutes. Reduce heat to 350 degrees, and continue baking until filling jiggles when shaken, about 30 minutes. Transfer pie to a wire cooling rack; let cool overnight.

5. Preheat oven to 450 degrees. Remove reserved grape leaves from refrigerator and brush with remaining egg and water mixture. Bake until golden brown, 15 to 20 minutes. Transfer to a wire cooling rack; let cool.

6. Before serving, place grape leaves on top of filling.