Cut out approx. 8 fruit flesh balls from the watermelon with a ball cutter. For the jelly, cut the remaining flesh from the skin and remove the seeds. Cut the flesh into cubes. Pour lemon juice and aperol over it and sprinkle with 100 g sugar. Chill for about 30 minutes.
Remove the seeds from the honeydew melon, peel it and use a peeler or a kitchen slicer to slice the flesh into 4-8 thin slices. Cut out balls from the remaining fruit flesh. Soak gelatine in cold water. Finely puree the marinated melon pulp and pour through a sieve. Squeeze out the gelatine and dissolve at lukewarm water. Stir 2 tablespoons of juice into the gelatine. Stir the mixed gelatine into the rest of the juice. Divide honeydew melon balls, up to 8 pieces, into 4 moulds (each containing 200 ml) and fill up with juice. Chill for approx. 2 hours. For the sabaione, whisk egg yolk, 50 g sugar and wine in an ovenproof bowl.
Stir the mixed gelatine into the rest of the juice. Divide honeydew melon balls, up to 8 pieces, into 4 moulds (each containing 200 ml) and fill up with juice. Chill for approx. 2 hours. For the sabaione, whisk egg yolk, 50 g sugar and wine in an ovenproof bowl. Whisk over a hot water bath with a whisk until thick and frothy. (The water must not boil!) Stir cold over a cold water bath. Remove the jelly from the moulds and arrange on plates with sabaione and melon balls. Dust with cocoa and decorate with melon slices and lemon balm leaves
waiting time approx. 2 1/4 hours