Stir together the jam and 4 tablespoons of the Grand Marnier in a small bowl to blend, set aside
Stir together the marscarpone and remaining 2 tablespoons of the Grand Marnier in a large bowl to blend. In electric mixer, beat the cream, sugar and vanilla until soft peaks form. Using a large rubber spatula, stir a fourth of the whipped cream into the mascarpone mixture. Fold in the remaining whipped cream into the mascarpone mixtue. Line the bottom of a very large bowl with one third of the ladyfingers. Spread one third of the jam mixture over the ladyfingers. Spread one third of the mascarpone mixture over the jam mixture, then cover with a third of the fresh raspberries. Repeat layering with the remaining ladyfingers, jam, mascarpone and raspberies. Cover and refrigerate at least 3 hours or overnight. Dust with conf. sugar before serving.