Mix mascarpone, yoghurt, lemon and orange juice. Grate one half of the orange peel, peel the other half thinly and cut into strips. Stir the grated peel, sugar and vanilla sugar into the cream.
Quarter melons, remove seeds and peel. Cut 1/4 of the Ogen melon into cubes, the rest into slices and net melon into triangles. Fold melon triangles under the mascarpone cream. Arrange slices of melon with the cream on plates.
Serve sprinkled with melon cubes and orange peel strips.