Pulse all-purpose flour, salt, and 2 teaspoons sugar in a food processor until combined. Add butter; blend until mixture resembles pebbles. Add ice water; pulse until mixture just comes together. Shape into a disk, wrap in plastic, and refrigerate 30 minutes or up to 2 days. In large bowl, stir together 2 tablespoons sugar and cornstarch. Add sliced white peaches, fresh lemon juice, and vanilla extract. Let stand 30 minutes to release juices. Preheat oven to 375°. Remove dough from fridge; let soften. Roll out onto parchment paper to 12 inches; transfer parchment paper with dough to baking sheet. Pile fruit mixture into center of dough; fold edges of the dough over fruit to make a seam. Brush edges of dough with beaten egg. Bake 45-50 minutes or until crust is golden and fruit is bubbling. Let cool, cut into 6 wedges, and serve.