Remove the seeds from the melon, cut out little balls using a melon baller (approx. 300 g). Stir in the currants and 1/2 tbsp of the icing sugar, cover and chill. Place the remaining fruit flesh and the remaining icing sugar in a pan. Add the lemon juice and vanilla seeds, simmer over a low heat for approx. 2 mins. Finely puree the mixture, leave to cool, then chill for approx. 30 mins.
To make the syllabub, place 100 ml of cold melon puree in a bowl. Add the cream and crème fraîche and beat to a firm, foamy crème with the whisk on a hand mixer. Divide the melon crème into dessert bowls. Arrange the fruit on top, drizzle over the remaining melon puree, serve immediately.