Butter with sugar and vanilla sugar, a pinch of salt mix well until it becomes a frothy cream. To which add the yolks one by one, chewing one by one. Put the beaten egg whites, put them spoon by spoon and mix with a wooden spoon from the bottom up. Add flour, mix. At the end add the milk.
Where is a tray of butter. Put the composition. Peeled apples are cut into slices and placed over the resulting top.
Sprinkle caster sugar and cinnamon over the apples. Bake for 40-45 minutes on the right heat.