For the base, knead flour, 100 g sugar, egg, butter, 1 packet of vanilla sugar and baking powder into a smooth dough. Roll out the dough on a baking sheet lined with baking paper and prick several times with a fork.
Roughly chop the marzipan for the topping. Add the ground and chopped hazelnuts and the cinnamon or 2 tablespoons of cognac and knead everything together.
Now bring the crème fraiche, 250 g sugar and 2 packs of vanilla sugar to the boil in a saucepan and then add to the hazelnut mixture. Now distribute the mass evenly on the rolled out floor.
Bake in a preheated oven at 175 ° C top / bottom heat (approx. 25 minutes.
Then let it cool down and cut into small nut wedges. Melt the couverture and decorate the cake with it as you like.