Preheat oven to 400 degrees. Brush 4 small ramekins with butter, making sure to coat thoroughly, including rims. Coat completely with sugar, gently tapping out any excess. In a mixing bowl whisk yolks, 1/4 cup sugar, and Grand Marnier until thoroughly mixed. Stir in melted chocolate. In another bowl, beat egg whites to soft peaks, add remaining sugar and beat just until stiff. Add half of whites to chocolate mixture, stirring to lighten mixture and incorporate completely. Gently fold in remaining whites, keeping batter as light as you can. Some white streaks may remain. Spoon batter into prepared ramekins.

Bake 8 to 10 minutes until puffed. Serve immediately, dusted with confectioners' sugar and pass warm chocolate sauce at table.