Combine whole-wheat flour, baking powder and baking soda in a medium-size mixing bowl and mix. Combine 2 eggs, melted butter, and vanilla extract in a larger mixing bowl and mix. Add milk to egg mixture and mix again. Add dry ingredients to wet while continuously mixing. Finally stir in 1 cup of mashed sweet-potatoes. Allow mixture to stand for 5 minutes to allow baking soda to react. Whip egg whites into stiff peaks and gently fold into batter. Ladle mixture into any style waffle-iron or make as pancakes if you don't have one. Cook until golden brown, or a bit darker than you may be used to due to the darker color of the whole-wheat flour and sweet-potatoes.