Spoon the biscuit crumbs into the bases of 4 glasses, pressing them down. Beat the quark and soft cheese together and stir in 2 tbsp of the icing sugar. Add the raspberries, squashing them into the mixture. Taste to check sweetness, adding more icing sugar if needed.
Carefully spoon the mixture on top of the biscuit crumb bases and then smooth flat. Chill until ready to eat. Decorate with a few extra raspberries if you like.