Heat the cherries with juice and 2 tablespoons of sugar. Stir the cornstarch with 2 tablespoons of water until smooth, mix into the cherries and bring to the boil while stirring. Let cool down.
Meanwhile, whip the cream until stiff. Put the quark, egg liqueur, vanilla sugar and remaining sugar, to taste, in a mixing bowl and stir. Carefully fold in the cream. Either chill or serve immediately.
Layer quark egg liqueur cream and cooled cherries in four dessert glasses.