Knead flour, baking powder, 100 g sugar, 1 vanillin sugar, salt, butter in pieces and egg first with the dough hooks of the hand mixer, then briefly with your hands until smooth. Roll out on a baking tray lined with baking paper (approx. 35 x 40 cm) and prick several times with a fork
Coarsely grate the marzipan into a bowl. Add cognac and nuts. Bring the crème fraîche, 100 g sugar and 2 vanillin sugars to the boil in a small pot over medium heat while stirring. Immediately pour over the nuts and stir everything together. Spread on the shortcrust pastry. Bake in the preheated oven (electric cooker: 175 °C/circulating air: 150 °C/gas: level 2) for about 25 minutes. Let cool off
Cut the biscuits into squares (approx. 4 x 4 cm) and cut them in half diagonally. Coarsely chop the couverture and melt separately in a hot water bath. Dip half nut corners with one corner each into the white, the other into the dark chocolate coating. Allow to dry