Mix the fat, sugar, vanilla sugar and salt until foamy, add the egg yolks and stir until the sugar has dissolved. Mix the flour with the baking powder, sieve and add alternately with the milk. Then stir in the sparkling water and carefully fold in the very stiffly beaten egg white.
Heat up the waffle iron, grease it, pour in the batter and bake the waffles until golden. Serve immediately sprinkled with powdered sugar or cinnamon sugar.