Remove seeds from the cantaloupe and carve with a melon baller. Carve the watermelon with a melon baller as well and combine with cantaloupe in a dish. Sprinkle with sugar, splash with Maraschino liqueur and refrigerate.
In the meantime, plump raisins in warm water (or tea) until soft. Chop shelled walnuts. When the melon balls are cold, combine with drained raisins and walnuts.
Arrange the fruit salad in 4 Martini glasses (or in bowls carved out of remaining cantaloupe peel). Whip heavy cream, fill a pastry bag with a star tip and garnish fruit salad. Sprinkle with grated chocolate, garnish with red currants and serve.