1Sift dry ingredients into a bowl. Add egg yolks to milk, mix well.Add the sweet potatoes and mix well. Beat egg whites until stiff and fold into the batter. Heat oil until very hot. Drop batter by spoonful into deep oil. Beignets will float when done. Remove from oil when light brown. Sprinkle half the beignets with powdered sugar ,the other half with cinnamon sugar.