Sift together the flour, sugar, baking powder and salt into a mixing bowl.
Beat the egg yolks until pale yellow.
Gently heat the milk and the sugar until the sugar dissolves.
Pour the egg yolks, cooled milk and the melted butter into the flour mixture.
Stir until smooth.
Set aside and allow to stand for at least an hour.
Beat the egg whites until stiff.
Carefully fold into the batter.
Fill a hot lightly oiled waffle iron two-thirds full with the batter and cook until the steam stops escaping. Serve with ice cream.