For the crust: In a stand mixer add, white rice flour, tapioca flour, potato starch, xanthum gum, salt, sugar, shortening, and butter. Blend until mixture has crumb type appearance, slowly add egg, vinegar, and water. Mix until combined, remove from bowl, divide dough into two balls, wrap both balls in plastic and form disks. Refrigerate for 45 minutes. Roll dough out into a 9 inch pie plate and bake on 400 degrees F for 15 minutes or until crust is golden. Cool completely.