Separate eggs. Beat the egg whites until stiff, add sugar and vanillin sugar. Add egg yolks bit by bit and stir in. Mix starch and flour, sieve over it and fold in carefully.
Grease the bottom of a springform pan (26 cm Ø), fill in the dough and smooth it down. Bake in a preheated oven (electric: 175 °C/ gas: level 2) for approx. 30 minutes. Let the sponge cake cool down, then cut through 2x horizontally.
Heat the jelly and spread it on the two lower sponge cake bases. Soak the gelatine. Whip cream until stiff. Mix quark, lemon juice and zest, sugar and egg yolk. Squeeze the gelatine, dissolve and gradually stir into the quark mixture.
Fold in the cream. Place the edge of the springform pan around the lower sponge cake base. Spread 1/3 of the quark mixture on top. Cover with the second sponge cake base. Fold mandarins, except for about 20 slices for decoration, into the remaining quark mixture.
Spread on the second sponge cake base and cover with the upper one. Leave to set in the refrigerator for about 2 hours. To decorate, whip cream until stiff and pour in sugar. Wash the lime and lemon and peel thinly with a julienne chewing tool.
Remove the springform pan rim from the cake. Spread half of the cream all around and decorate with a serrated comb. Pour the rest of the cream into a piping bag with a star-shaped spout and squirt 12 cream tuffs onto the edge of the cake.
Decorate tuffs and cake centre with mandarin slices and lime and lemon peel. Makes about 12 pieces.