Soak gelatine in cold water. In the meantime, wash the grapes and pluck the berries from the stems. Sort the raspberries. Mix buttermilk, lemon juice and 100 g sugar well. Rinse 4 moulds (each containing 150 ml) with cold water and distribute the grapes evenly.
Heat the squeezed gelatine in a pot (do not boil) while stirring continuously, carefully stir into the buttermilk, fill into the moulds and refrigerate for approx. 4 hours. Put half of the raspberries aside, puree the remaining raspberries, remaining sugar and vanilla sugar. Turn out the jelly and arrange on four plates with raspberry puree and raspberries. Serve decorated with lemon balm as desired