Separate the eggs for the dough. Beat the egg whites, salt and 3 tablespoons of cold water with the whisks of the hand mixer until stiff. Gradually add sugar and 1 packet of vanilla sugar. Stir in egg yolk. Mix flour, starch and baking powder, sieve onto the egg mixture and fold in carefully. Line the bottom of a springform pan (26 cm Ø) with baking paper.
Fill in sponge cake mixture and smooth it down. Bake in the preheated oven (electric: 200 °C/ gas: level 3) for 18-20 minutes. Remove from the oven, remove from the edge with a sharp knife and let cool on a grid. In the meantime, drain mandarins well on a sieve. Coarsely chop the chocolate coating and melt in a water bath. Let it cool down a little. Remove the base from the mould and cut through 1x. Put some mandarin oranges aside for decoration. Sprinkle the bottom layer with rum and cover with mandarin oranges. Fill half of the cream into a mixing cup, whisk until stiff with the whisks of the hand mixer. Add 1 packet of vanilla sugar and half of the melted chocolate coating.
Let it cool down a little. Remove the base from the mould and cut through 1x. Put some mandarin oranges aside for decoration. Sprinkle the bottom layer with rum and cover with mandarin oranges. Fill half of the cream into a mixing cup, whisk until stiff with the whisks of the hand mixer. Add 1 packet of vanilla sugar and half of the melted chocolate coating. Do the same with the remaining cream, remaining vanilla sugar and remaining couverture. Spread a good 1/3 of the chocolate cream on the mandarin oranges. Place the cake lid on top and spread with the rest of the cream. Cover with the mandarin oranges that have been put aside. Serve decorated as desired with lemon balm and chocolate flakes
Do the same with the remaining cream, remaining vanilla sugar and remaining couverture. Spread a good 1/3 of the chocolate cream on the mandarin oranges. Place the cake lid on top and spread with the rest of the cream. Cover with the mandarin oranges that have been put aside. Serve decorated as desired with lemon balm and chocolate flakes