Cooking Steps

1. Preheat oven to 350°F. In a bowl sift together the flour, baking powder, 1 teaspoon granulated sugar, and salt. Using a fork, work in the shortening until mixture resembles coarse crumbs. Slowly add buttermilk to flour mixture blending until incorporated. Work with hands to form dough into a ball. Cut dough ball in half.
2. On a lightly floured surface roll out one half into a 14 x 12" rectangle. Spray a 13 x 9 x 2" baking dish with nonstick cooking spray. Place dough in baking dish, halfway up the sides. Prick entire bottom and sides of dough with a fork bake for 4 minutes or until golden. Set shell aside.
3. Drain peaches; reserve liquid. Place peaches in a pot; add 2 cups of the reserved liquid. Add the 2 cups granulated sugar, the brown sugar, butter, cinnamon, nutmeg, and vanilla. Cook on medium heat for 5 to 6 minutes. In a glass measure mix together cornstarch, water, and lemon juice; add to peach mixture. Cook over low heat for 4 minutes more. Remove from heat. Pour mixture into baked shell
4. Roll out the second half of the dough and cover the top of the filling. Randomly make about 6 to 7 slashes into the dough about 1/2 inch long. Mix together egg and water to make an egg wash. With pastry brush, brush egg wash over top of crust. Sprinkle 1 teaspoon granulated sugar over crust. Place in oven and bake for 30 to 45 minutes or until crust is golden. 
5. Note: your dough may not roll out to form a perfect rectangle. Try to get as close as you can and trim off the edges where necessary. Before placing the dough on top, fold it in half carefully. Lay it on top of the peaches, then unfold the dough and seal the edges