Place the halved strawberries in a bowl. Sprinkle 1 tbsp. sugar over the berries. Stir in 4 tbsp. Grand Marnier. Place bowl in refrigerator and let “marinate” for 6 hours.
Stir the strawberry jam and 4 tbsp. Grand Marnier in a small bowl to blend.
Using an electric mixer, blend the mascarpone cheese and remaining Grand Marnier in a large bowl. Again, using an electric mixer, beat the cream, remaining sugar, and vanilla in another large bowl until soft peaks form. Stir about 1/4 of whipped cream into a mascarpone cheese mixture, and then fold in the remaining whipped cream.
Line the bottom of a 9 x 13 glass dish with one of the sliced pound cakes. Spread half of the mascarpone cheese mixture over the jam mixture. Layer half of the strawberries over the mascarpone cheese mixture. Repeat the layers starting with the sliced pound cake and finishing with the other half of the strawberries.
Cover and refrigerate overnight. The mascarpone cheese gives this classic an Italian twist!