Beat the butter, sugar, gingerbread spice, vanilla sugar and salt until frothy. Add the eggs one by one and continue to beat.
Mix the hazelnuts, flour and baking powder, add to the mixture and fold in.
Place the dough on a baking sheet lined with baking paper and smooth it out. Bake in the preheated oven for 20-25 minutes at 175 °. Remove the cake and let it cool down.
For the sauce, stir together the cold mulled wine and powdered sugar.