From Joan Edwards 

1/2 cup butter
1-1/4 cups sugar
1-1/2 cups sweet potatoes, cooked & mashed (or 1 can, drained)
2 eggs
1 cup milk
1-1/2 cups flour
tsp cinnamon
1/4 tsp salt
1/2 tsp nutmeg
2 tsp baking powder

Cream butter, sugar & sweet potatoes until smooth.  Add eggs.  Blend dry ingredients well.  Add alternately with milk to egg batter.  Do not over mix.  Gently fold in chopped pecans or walnuts, coconut, chocolate or peanut butter chips, raisins or anything you especially like.  I probably end up with 1-1/2 cups combined extras.  Spoon into greased muffin tins and sprinkle a little cinnamon-sugar on top before baking.  Bake at 375 about 25 minutes.  Makes 24 small muffins.  Freeze well and reheat well.