In a food processor place flour, sugar, and salt. Pulse just to combine dry ingredients. Sprinkle butter pieces and shorteninng over the dry ingredients and pulse to form a very coarse cornmeal-like mixture. Transfer to a mixing bowl and sprinkle with water. Mix to combine. The dough will still be crumbly.
Pour onto parchment or plastic wrap. Using the wrap, pull up the sides to create a cohesive dough. Form disk and pat into a flat round. Chill for 15-20 minutes. Roll out to fit a 9-inch pie pan. If the dough becomes too soft, place back in the refrigerator to chill. Fill with your desired pie filling and bake according to the recipe.
If you want to fully bake the crust preheat the oven to 375°F. Line the chilled crust with parchment and weights filling up the interior of the shell (or dried beans as weights). Bake with weights until the outer crust is set, 15-20 minutes. Remove the parchment and weights, dock the crust and continue to bake until the inside crust is golden, 20-25 minutes.
For an all-butter crust, simply swap the vegetable shortening for 4 tbsp unsalted butter, bringing the total amount of butter to 10 tbsp.