Sweet Potato Biscuits

2 T  light brown sugar
1 t.  salt
2 C  all purpose flour
1/2t. baking soda
2 t.  baking powder
3/4 C buttermilk
1/2 C margarine, melted
3/4 C mashed cooked sweet potatoes

Preheat oven to 400 degrees.   Sift together flour, baking powder, and salt.  Combine brown sugar, melted margarine, and sweet potatoes in a small bowl, best until fluffy.  Stir soda in buttermilk.  Combine all ingredients.  Stir only until moist.  Turn out on a floured surface.  Knead slightly.  Roll out and cut into biscuits.  Bake on ungreased baking sheet for 20 minutes or until done.