Sift together the flour, baking soda, baking powder and add salt and sugar. Set aside. In a small bowl combine the egg yolks, buttermilk, milk and melted butter. Using a rubber spatula, gently fold the liquid into the dry ingredients. In a separate bowl, beat the egg whites until they are foamy and hold soft peaks. Gently fold the egg whites into the batter.
The buttermilk in this recipe adds a touch of lightness to the waffles. For extra flavour, try adding mashed banana and cinnamon, blueberries or sliced cooked apple to the batter mix.