Sift together flour, baking powder and salt. Cut in shortening with fork or pastry cutter. Combine warm sweet potatoes and sugar, mixing well. Add milk.Combine sweet potato and flour mixtures. Blend well. Place on floured  surface and roll to desired thickness or about 1/2 inch thick. Cut with biscuit cutter.Bake on lightly greased baking sheet at 400 degrees for 10 minutes. Yields 2 to3 dozen.