Separate eggs, beat egg whites and 4 tablespoons of water until stiff. Finally pour in sugar and vanilla sugar. Stir in the egg yolks one after the other. Flour. Mix cornstarch, baking powder and cocoa.
Sieve onto the egg foam mixture and fold in loosely. Spread on a baking tray lined with baking paper and bake in a preheated oven (electric: 200 °C / gas: level 3) for 10-12 minutes. Immediately turn onto a clean, damp tea towel and remove the baking paper.
Wrap the sponge cake in the cloth and let it cool down. Soak gelatine in cold water. Drain the mandarins. Squeeze the gelatine, dissolve and mix with 150 ml advocaat. Chill for 5-10 minutes.
In the meantime, beat 250 g cream and vanillin sugar until stiff. Fold in the cream as soon as the advocaat starts to gel and spread it on the sponge cake. Add mandarins, except for 12 pieces for decoration, and roll up from the short side.
Cover and put in a cool place for about 6 hours. Whip the rest of the cream and sugar until stiff and spread half of the sponge roll on top. Cut roll into 10-12 pieces. Put the rest of the cream in a piping bag with a star-shaped spout and decorate each piece with a cream tuff.
Sprinkle the tuffs with the remaining egg liqueur and serve decorated with the remaining mandarins. Makes 10-12 pieces.