Pinch the mixture together with your fingertips until it resembles the texture of damp sand. Add the egg and stir, and add the water, a tablespoon at a time, mixing it with a fork, until the dough just holds together when you squeeze a fistful of it in your hand. Press the dough into a greased deep-dish 10-inch wide and 1.75-inch deep tart shell or a greased 9-inch wide 2-inch deep pie pan to form the crust. Poke the bottom with a fork and place the pan in the freezer for 30 minutes.