Drain the cherries, collect the juice. Mix starch and 4-5 tablespoons of juice. Boil up the rest of the juice. Stir in the starch and bring to the boil. Fold in cherries and let cool down
Cut the cake into small pieces. Put it in a bowl. Whip the cream until stiff, sprinkle with vanilla sugar and cream thickener. Mix 2/3 with yoghurt. Layer with cherries on the cake. Decorate with the rest of the cream, chocolate shavings and lemon balm