Cream 125 g butter, vanillin sugar and 120 g sugar with the whisk of the hand mixer. Stir in the eggs one after the other. Mix flour and baking powder and alternately stir in 2 tablespoons of milk. Halve the dough and stir in the cocoa under one half. Pour both doughs separately into piping bags. Grease a hinged box form (30 cm long).
Spray doughs side by side in thumb-thick rolls lengthwise onto the bottom. Repeat the process until the bottom is covered. Spread the blueberries on the dough and press in lightly. Bake in the preheated oven (electric range: 175 °C/ convection oven: 150 °C/ gas: level 2) for 25-30 minutes. In the meantime, stir pudding powder, 50 g sugar and approx. 6 tablespoons milk until smooth. Bring 440 ml milk to the boil, remove from the heat, stir in the pudding powder and simmer for another 1 minute. Put it into a bowl, cover the surface directly with foil and let it cool down. Remove the cake from the oven and let it cool down. Whip 250 g butter until creamy white. Stir the pudding at room temperature (butter and pudding must have the same temperature!!) briefly and add to the butter by the spoonful, stirring continuously. Spread the butter cream on the cake and refrigerate for approx. 3 hours. Coarsely chop the chocolate coating.
Put it into a bowl, cover the surface directly with foil and let it cool down. Remove the cake from the oven and let it cool down. Whip 250 g butter until creamy white. Stir the pudding at room temperature (butter and pudding must have the same temperature!!) briefly and add to the butter by the spoonful, stirring continuously. Spread the butter cream on the cake and refrigerate for approx. 3 hours. Coarsely chop the chocolate coating. Melt the couverture and coconut oil in a bowl over a warm water bath. Let the chocolate coating cool down for about 15 minutes, then spread it on the cake. Use a cake comb/ serrated pastry sheet to draw wavy stripes through the couverture. Refrigerate again for about 30 minutes until the chocolate icing is firm. Open the box form and cut the cake into 14 slices. Decorate with chocolate shavings
Melt the couverture and coconut oil in a bowl over a warm water bath. Let the chocolate coating cool down for about 15 minutes, then spread it on the cake. Use a cake comb/ serrated pastry sheet to draw wavy stripes through the couverture. Refrigerate again for about 30 minutes until the chocolate icing is firm. Open the box form and cut the cake into 14 slices. Decorate with chocolate shavings