Separate eggs, whisk egg whites and 4 tbsp. water until stiff. Beat in sugar and vanilla sugar. Fold in egg yolks one by one. Mix baking powder, flour, cornstarch and cocoa. Sift onto egg mixture and fold in. Spread dough on a baking sheet lined with parchment paper. Bake in a heated oven (electric oven: 200 °C /gas: level 3) for 10-12 minutes. Immediately turn out onto a damp tea towel and remove the parchment paper. Roll up the sponge cake from the short side using the cloth and cool. Soak the gelatine in cold water. Drain the manadarines. Squeeze gelatine, let it melt and stir with 150 ml egg liqueur. Leave to cool for 5-10 minutes. In the meantime, whip 250 g cream and vanilla sugar until stiff. As soon as the eggnog starts to gel, fold in the whipped cream and spread on the sponge cake. Add the mandarins, except for 12 pieces for decoration, and roll up the sponge repeatedly. Cover and refrigerate for approx. 6 hours. Whip remaining whipped cream and sugar until stiff and spread half of it on the sponge cake roll. Cut roll into 10-12 pieces. Put the rest of the whipped cream in a piping bag with a star-shaped nozzle and decorate each piece with a cream tuff. Drizzle tuffs with remaining eggnog and decorate with remaining tangerines.
Preparation : 1 hour without waiting