Place flour, salt, and baking powder in the Cuisinart™ mixing bowl. Insert the flat mixing paddle. Mix on speed 1 for 15 to 20 seconds. Sprinkle half the butter and all the shortening over the flour mixture. Mix on speed 1 for 45 seconds. With the stand mixer running, add the remaining bits of butter and mix until the mixture resembles crumbs but still with pea-sized bits of butter visible, about 45 to 60 seconds longer. With the stand mixer running, add the minimal amount of ice water, one tablespoon at a time. Stop mixing just when the mixture begins to form a ball. Turn off stand mixer.
Using hands gather up into a ball (2 balls for a two-crust recipe). Flatten into a disc about 6 inches in diameter and cover tightly with plastic wrap. Chill for at least 1 hour before using to allow the glutens in the flour to rest.
The dough will keep refrigerated for up to 3 days, or may be frozen (double-wrapped) for up to a month (thaw at room temperature for an hour before using).
To blind bake the pastry for a single-crust filled pie or tart, roll out pastry 1⁄8 inch thick to fit pan, crimp and seal edges. Prick bottom all over with a fork. Chill for 30 minutes.
Preheat the oven to 400ºF. Line crust with a sheet of aluminum foil or parchment paper and fill with pie weights, dry rice or beans. Bake for 15 minutes.
Note: For a sweeter piecrust add 1 or 2 tablespoons granulated sugar to the flour mixture in the beginning of the recipe.