Defrost the berries. Place the cake ring (24 cm Ø) on a slightly oiled cake plate. Put the rusk into the bag, close it and crumble finely. Melt butter and mix with crumbs. Spread as a base on the plate, press on. Chill for 1 hour
Soak the gelatine in cold water. Puree 100 g berries, pass through a sieve. Mix with quark, cream cheese and sweetener. Squeeze the gelatine, dissolve. First stir in some cream, then stir into the rest of the cream. Whip cream until stiff, fold in. Spread on the base. Chill for at least 4 hours.
Boil the rest of the berries and 5 tablespoons of water. Stir starch and 1 tablespoon of water until smooth, bind berries and sweeten. Cool down. Pour onto the cream. Cool for about 1 hour.