In a large mixing bowl, combine the cold flour, cream of tartar, and salt.
Cut in Crisco:
Add the cold Crisco to the flour mixture. Using a pastry cutter or your hands, cut the Crisco into the flour until the mixture resembles coarse crumbs.
Prepare Liquid Mixture:
In a small bowl, mix the very cold water, well-beaten egg, and vinegar.
Combine Mixtures:
Gradually add the egg mixture to the flour and Crisco mixture, 1 tablespoon at a time, gently mixing with a fork or your hands. Continue to add the liquid until the dough just comes together. You may not need all the liquid.
Divide and Chill:
Once the dough comes together, divide it into two equal portions. Shape each portion into a disc, wrap in plastic wrap, and refrigerate for at least 30 minutes to chill.
Roll Out Dough:
When ready to use, remove one disc of dough from the refrigerator. On a lightly floured surface, roll out the dough to fit your pie dish. Repeat with the second disc if making a double-crust pie.
Assemble Pie:
Place the rolled-out dough into your pie dish and trim any excess dough from the edges. If making a double-crust pie, fill the pie with your desired filling, then place the second rolled-out dough on top. Trim, seal, and crimp the edges as desired.
Bake:
Follow the baking instructions for your specific pie recipe.