For the mulled wine cake, cream butter with powdered sugar and egg yolks until fluffy. Mix in the melted chocolate and the cold mulled wine.
Flavor with allspice, cinnamon and ginger. Beat egg whites with granulated sugar until stiff and fold into the mixture. Finally, carefully incorporate flour and baking powder. Butter a cake pan and pour in the mixture.
Bake in the preheated oven at 180 °C for about 50 minutes. After baking, turn out onto a cake rack, let cool and sprinkle with powdered sugar.