Stir together flours, xanthan gum, salt and sugar. Cut margarine and shortening into small chunks until you have small pieces distribute throughout the flour.
Add vinegar/lemon juice and ice water. Stir into flour mixture until it forms a ball. Turn out onto a lightly floured board and knead a few times. Divide into two, and wrap into parchment paper, and chill at least one hour or overnight.
Once you take it out of the fridge, let sit for five minutes. Roll out on floured board. Or, I actually just plop it into the pie pan and use my hands to get it right. I prebake crust by pricking the shell with a fork then bake for 10 - 12 minutes in a preheated 450 degree oven.
The vinegar or lemon juice replaces 1 egg. It can be omitted.
Margarine can be replaced with 1/2 cup canola oil.
If you have other flours you like to use, just remember that it has to add up to 2 1/2 cups.
Butter and Margarine: Butter is a dairy product made from cow’s milk. Margarine typically contains milk or soy, but there are milk-free and soy-free versions available.
Corn Substitutions: Corn is a common ingredient in products. Starch, modified food starch, dextrin and maltodextrin can be from corn. Consult with your physician to find out which corn derivatives you need to avoid. Many corn-free options are available in the US. Find out more about corn substitutions.
Gluten: Gluten is a protein found in specific grains (wheat, spelt, kamut, barley, rye). Other grains are naturally gluten-free but may have cross-contact with gluten-containing grains. Look for certified gluten-free products if you need to avoid gluten. Find out more about wheat and gluten substitutions.
Milk and Soy Substitutions: Alternative dairy-free milk beverages and products will work in most recipes. Find out more about milk substitutions and soy substitutions.