Gluten Free Buttermilk Biscuits With Sausage Gravy

1 ½ pound bulk pork sausage 1 cup chopped onion (1 large) ¼ cup Gluten-Free Flour Mix 3 cup milk Salt and black pepper 2 teaspoon snipped fresh thyme

Gluten Free Flour Mix

3 cup white rice flour 3 cup potato starch 2 cup sorghum flour 4 teaspoon xanthan gum