In a medium bowl sift together the flour, 3 tablespoons sugar and salt. Work in the copha 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 180 degrees C. Roll out half of dough to 3mm thickness. Place in a 20x30cm 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 125g butter and cook over medium-low heat until butter is melted. In a mixing bowl, stir together 2 cups sugar, nutmeg, cinnamon and cornflour; mix into peach mixture. Remove from heat and pour into baked crust.
Roll remaining dough to a thickness of 5mm. Cut into 1 cm 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 to 40 minutes, or until top crust is golden brown.