Grease the bottom and rim of a springform pan (24 cm Ø). Crush the biscuits in the universal chopper. Melt butter. Mix crumbs and butter and press them against the bottom and rim of the springform pan. Refrigerate the base for about 10 minutes.
Chop the chocolate and melt in a bowl over a warm water bath. Mix cream cheese, quark, vanillin sugar and 100 g sugar. Stir melted chocolate and starch into the cheese mixture. Stir in the eggs one by one. Stir in cocoa. Pour the cheese mixture into the springform pan. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: see manufacturer) for about 15 minutes. Reduce oven temperature (electric oven: 150 °C/ convection oven: 125 °C/ gas: see manufacturer) and bake for approx. 1 hour more
Turn off the oven, open the door and let the cake rest in the oven for another 10 minutes. Take out the cake, remove from the edge and let it cool down on a cake rack
Just before serving, beat the egg whites until stiff, adding 100 g of sugar and beating until the sugar has dissolved. Place the beaten egg whites in the middle of the cake, leaving about 1 cm free at the edge. Bake the cake under the hot grill for 5-10 minutes until golden brown
Waiting time approx. 10 minutes