In a medium bowl, sift together the flour, 3 tablespoons sugar, and salt. Work in the shortening with a pastry blender until the mixture resembles coarse crumbs. In a small bowl, whisk together the egg and cold water. Sprinkle over flour mixture, and work with hands to form dough into a ball. Chill 30 minutes.
Preheat oven to 350 degrees F (175 degrees C). Roll out half of dough to 1/8 inch thickness. Place in a 9x13 inch baking dish, covering bottom and halfway up sides. Bake for 20 minutes, or until golden brown.
In a large saucepan, mix the peaches, lemon juice, and orange juice. Add 1/2 cup butter, and cook over medium-low heat until butter is melted. In a mixing bowl, stir together 2 cups sugar, nutmeg, cinnamon, and cornstarch; mix into peach mixture. Remove from heat, and pour into baked crust.
Roll remaining dough to a thickness of 1/4 inch. Cut into half-inch-wide strips. Weave strips into a lattice over peaches. Sprinkle with 1 tablespoon sugar, and drizzle with 1 tablespoon melted butter.
Bake in preheated oven for 35-40 minutes, or until top crust is golden brown.