Mix the flour, sugar, vanilla sugar and salt. Dissolve the yeast in lukewarm milk and mix with the flour. Cover the dough and let it rise for 10 minutes.

Separate the eggs, beat the egg whites until stiff.

Let the butter melt slowly in a saucepan, let it cool down, then add the egg yolks and butter to the dough and let rise for another 20 minutes.

Finally fold in the egg whites and quickly bake in the waffle iron on the highest setting