Peel the orange so that the white skin is completely removed. Remove the fillets with a sharp knife between the parting skins. Press the juice from the parting skins into a bowl.
Wash and halve the grapes. Apple wash, halve, remove seeds. Cut apple halves into small pieces. Peel and slice the banana. Mix fruit with orange liqueur and 1 teaspoon sugar.
Melt the chocolate over a warm water bath, let it cool down lukewarm. Pour fruit salad into 4 glasses. Whip cream until semi-stiff. Mix mascarpone, vanilla sugar and 1 teaspoon sugar with a whisk of the hand mixer
Fold in the cream. Fold the liquid chocolate into the mascarpone cream and immediately pour into the glasses on top of the fruit salad.