Sift together the flour, baking powder, salt and nutmeg into a mixing bowl.
Beat the egg yolks until pale yellow, then add the milk and beat well.
Pour the egg yolk and milk mixture onto the flour and blend thoroughly.
Stir in the melted butter or vegetable oil.
Set aside for at least an hour.
Mix the mashed bananas with the batter.
Beat the egg whites until stiff and fold into the banana batter.
Fill a hot, lightly oiled waffle iron two-thirds full with the batter and cook until the steam stops escaping from the sides.