Combine 8 ounces of chocolate and Grand Marnier in a heavy saucepan; cook, stirring constantly, over low heat until chocolate melts. Remove from heat, and cool to lukewarm.
Beat whipping cream until foamy; gradually add powdered sugar, beating until soft peaks form. Gently fold about 1/2 cup of whipped cream into chocolate; fold in remaining whipped cream. Spoon into individual serving dishes. Chill until ready to serve. Must be kept cold.
So easy and delicious, this dessert returns year after year to our Christmas table. It is very rich, so a small portion goes a long way.