Preheat the oven to 400º F. Using the butter, grease 4 individual ramekins and sprinkle them with about 1/2 teaspoon sugar per ramekin.

In a large metal bowl set over a pot of simmering water, melt the chocolate, stirring it with a whisk from time to time. Remove the bowl of melted chocolate from the heat.

Using an electric mixer, beat the egg whites until frothy.  With the mixer still running, add 1/4 cup of the remaining sugar and continue to beat until just stiff and glossy.  Do not overbeat (when whites lose their sheen).

Whisk the egg yolks into the chocolate one at a time, add the Grand Marnier, and whisk in the remaining sugar. Gently fold in the egg whites, passing a large whisk through the mixture once or twice to make sure it is thoroughly blended.

Pour the chocolate mixture into the prepared ramekins, place on a baking sheet, and bake until puffed and somewhat firm, about 20 minutes. Remove from the oven.

While the soufflés are baking, prepare the Chocolate Grand Marnier Sauce, and cover to keep warm.  As an option to passing the sauce,  you can serve each guest their own portion of the sauce to add to their soufflé as desired.

To serve, place a ramekin on each of four small plates and sift confectioners' sugar over the top.  Ask your guests to break the tops of their soufflé with a spoon and pour in the warm Chocolate Grand Marnier Sauce, allowing it to drip over the sides.