Marinate blackberries with vanilla sugar, sugar and Grand Marnier (or orange juice) for thirty minutes.
Crush a quarter of the berries. Beat the egg yolks, honey and berry marinade (*) in a baking bowl in a hot water bath with a whisk until you get an airy cream (do not make in any case). Place the cream in a cold water bath and whip until cooled.
Stir the mascarpone into the cooled mixture. Fold in the blackberry puree and the blackberries.