Put the biscuits in a freezer bag and crush them with a rolling pin. Roughly chop the dark chocolate couverture and melt it together with the butter over the water bath.
Line the bottom of a 20 cm springform pan with parchment paper. Mix the liquid chocolate with the biscuits, spread it on the base and press it down. Chill for 20 minutes.
Soak the gelatine in cold water.
Whip the cream until stiff. Then stir in the vanilla sugar, sugar, low-fat quark and cream cheese.
Squeeze the water out of the gelatin and dissolve it in a saucepan or in the microwave over low heat. Mix 5 tablespoons of the cream with the gelatin and then the whole cream.
Spread half of the cream on the biscuit base. Then the fruit pulp and then the rest of the cream. Chill the cake for at least 4 hours. Then carefully remove from the springform pan.