Put your butter through your box grater, or whatever type of grater you use. Put the butter and shortening into a small bowl and beat together until smooth. The butter shreds will still show as shreds. Cover bowl and place in refrigerator until mixture is firm.
Sift together flour, sugar and salt in medium bowl.
NOTE: If you are making a sweet crust you will add the sugar now. Do not add sugar for a savory dough.
Once the butter mixture is firm, using a fork or a pastry cutter, cut it into the dry ingredients until mixture has a consistent texture.
Mix egg yolk, ice water and vinegar into dough, then form into ball and refrigerate about 1 hour.
Preheat oven to 450° F.
When dough has chilled, roll it out and press into pie plate. Press parchment paper or aluminum foil into crust and weight crust down with ceramic pie weight or another pie plate filled with dried beans.
Bake 15 minutes, then remove weights or pan filled with beans and prick crust with fork to allow steam to escape. Bake another 5−10 minutes or until crust is golden brown. Let crust cool before filling.
NOTE: If you are making a double crust pie simply double the recipe. Forego the precook on the crust, fill the uncooked crust, top with the second crust and bake.