Sort the blackberries, wash them and pat dry with kitchen paper. Put 4 berries aside.
Puree the remaining berries with the lemon juice, powdered sugar and 1/2 packet of vanilla sugar in the food processor. Then mix in the milk, quark and ice cream, so that a foamy liquid is formed. Whip the cream until stiff, whipping in the rest of the vanilla sugar. Fill into a piping bag with a star nozzle. Pour the fruit drink into four glasses. Pour cream into each glass and garnish with the set aside blackberries.