Cream butter, 200 g sugar, vanillin sugar, lemon zest and eggs with the whisks of the hand mixer. Add milk, 60 ml Prosecco and mix. Mix flour, salt and baking powder and stir into the egg-sugar mixture in portions. Pour the dough into a greased springform pan (26 cm Ø), dust with flour, smooth it down and bake in a preheated oven (electric range: 175 °C/ convection oven: 150 °C/ gas: level 2) for approx. 40 minutes. Remove from the oven, place on a cake rack and let cool off
Soak gelatine in cold water. Select the blueberries, wash and drain well. Wash the currants and, except for approx. 300 g, strip them from the panicles. Remove the bottom from the mould. Cut a thin lid off the bottom and crumble. Cover and put aside. Place the cake ring around the base
Mix quark, 100 g sugar and 160 ml prosecco. Squeeze the gelatine and dissolve over a warm water bath. Mix the gelatine with the rest of the Prosecco, stir into the quark mixture and chill for about 15 minutes until the quark mixture begins to gel
Whip the whipped cream with the whisk of the hand mixer until stiff and fold into the quark cream. Carefully stir in the berries and 1/2 cake crumbs. Spread the mixture on the base, smooth it down and put it in a cool place for about 3 hours. Remove cake ring. Decorate the cake with the remaining crumbs and currants
waiting time approx. 4 hours