Wash, halve and stone the plums. Steam plums in 1/8 litre water and sugar for 10 minutes. Stir cornflour and some water until smooth and add to the plums. Bring to the boil again.
Put the plum compote in a bowl and let it cool down. Keep 2 tablespoons of plums for decoration. Whip the cream, vanilla sugar and slivovitz until semi-stiff and pour over the cooled plums.
Decorate with remaining fruit and lemon balm. Sprinkle with some cinnamon.