1/3 c. Potato starch/flour
1/3 c. Tapioca flour
1/3 c. Rice flour
1/3 c. Almond flour
1/2 tsp. salt
1 tsp. xanthan gum
1/2 c. cold butter, cut into pieces
1 beaten egg
1 tsp. vinegar
If you don't have almond flour, double the rice flour to 2/3 cups.
Use a food processor and whir up the butter with all the flours, salt and xanthan gum.
After the mixture is crumbly, drop in the beaten egg into the mixture and whir again. Now scrape down the edges of your food processor to release some of the butter/flour that might be sticking to the sides and bottom.
Add in the vinegar and continue whirring the mixture.
Check to see if the mixture has the right consistency. If it doesn't, you can add in egg whites (I always have a carton of egg whites in the house).
Don't over process or add too much liquid. You can tell the consistency is right when you can squish the mixture together.
Put out on a pastry board and roll it out.