Beat the eggs, 5 tablespoons of lukewarm water, sugar and vanillin sugar in a mixing bowl until creamy. Sift the flour, starch and baking powder over the egg mixture and carefully fold in with a whisk.
Line the bottom of a springform pan (26 cm Ø) with baking paper, fill in the dough and bake in a preheated oven (electric range: 175 °C/ convection oven: unsuitable/ gas: level 2) for 30-40 minutes. Remove the sponge cake base from the tin and let it cool down.
For the cream, take off about 1/8 litre of the milk and stir the pudding powder into it until smooth. Put the remaining milk, sugar and salt in a pot and bring to the boil. Add the pudding powder while stirring and bring the pudding to the boil.
Cover the pudding with foil and let it cool down. Beat butter and icing sugar until fluffy. Add the pudding by the spoonful and stir in. Fill a piping bag with star-shaped spout with 1/4 of the buttercream and put it in the fridge.
Cut the sponge cake base twice. Spread 3 tablespoons of quince jelly evenly on the lower cake base. Place the second cake base on top and spread with 4 tablespoons of butter cream. Cover the cake with the last cake base, spread the top and sides with the remaining cream.
Mark with a cake divider (16 pieces). Sprinkle the cake edge and approx. 1 1/2-2 cm of the cake cover with brittle. Spread the remaining quince jelly in the middle and decorate the cake with the remaining buttercream in a piping bag.
Makes 16 pieces.