Drain the plums and collect the juice. Mix 3 tablespoons of juice and starch. Boil up the rest of the juice, lemon peel and 2 tablespoons of sugar. Stir in the starch. Add the plums and let it cool down. Remove lemon peel.
Mix quark and yoghurt. Add remaining sugar, vanilla sugar and lemon juice. Stir in chocolate crumble. Coarsely crumble the lady fingers. Arrange quark, compote and ladyfingers on dessert plates. Decorate with lemon balm leaves and chocolate sprinkles as desired