Cream butter, sugar, vanillin sugar and salt. Stir in the eggs one after the other. Mix flour, baking powder and 200 g hazelnuts and alternately stir into the egg-sugar mixture with 75 g cream. Grease the fat pan of the oven (35 x 30 cm) and dust with flour. Spread the dough on top to smooth it down.
Bake in the preheated oven (electric oven: 175 °C/ convection oven: 150 °C/ gas: level 2) for 30-35 minutes. Let cool down on a cake rack. Meanwhile, roast 150 g hazelnuts in a pan without fat, let cool again. Whip 600 g cream and cream firmer until stiff. Stir in cooled hazelnuts. Spread the cream on the cake. Knead marzipan and icing sugar. Take a piece of marzipan about the size of a tablespoon aside. Roll out the rest of the marzipan between cling film to form a sheet the size of the baking tray. (If it is too difficult, roll out 2 smaller plates [30 x 17.5 cm each]). Place the marzipan cover on top of the cream using the foil.
Knead marzipan and icing sugar. Take a piece of marzipan about the size of a tablespoon aside. Roll out the rest of the marzipan between cling film to form a sheet the size of the baking tray. (If it is too difficult, roll out 2 smaller plates [30 x 17.5 cm each]). Place the marzipan cover on top of the cream using the foil. Roll out the rest of the marzipan thinly as well and cut out small flowers. Spread on the cake. Decorate with hazelnut kernels and dust with icing sugar