In another bowl, sift sorghum flour, potato starch, tapioca flour, xanthan gum and baking powder. Mix the sugar and margarine mixture in with the flours until you get dough. The dough may be too sticky to handle. If that is the case, add a little more sorghum flour to it. It's okay if it is a little sticky, as long as you can work it easily with your hands. Form the dough into a patty and put in the refrigerator or freezer to chill.