I use the recipe directly from my betty crocker cookbook, and where it calls for 2 cups flour, I use a mix of 4 different kinds of GF flours (1/2 cup each), and a tsp-ish of xantham gum. For the topping, where it calls for 1/2 cup flour, I just use rice flour.
Wow, it always tastes as good as I remember (I don't have a chance to make it very often).
