Melt chocolate with ¼ cup strong coffee in top of a double boiler, stirring often. Remove the top of the double boiler. Beat the softened butter into the smoothly melted chocolate. One by one, beat in the egg yolks. Set aside.

In a separate chilled bowl, beat the cream until it leaves light traces on the surface. Set aside.

In a large mixing bowl, beat the egg whites (make sure that the beaters are clean) until they form soft peaks. While beating, sprinkle sugar by spoonfuls and continue beating until stiff, shining peaks are formed. Scrape chocolate mixture down the side of the egg-white bowl, and delicately fold them together. When almost blended, fold in the whipped cream.

Turn the mousse into an attractive serving bowl. Cover and chill for several hours. Serve with a swirl of whipped cream. Yield: 8 servings.

*Note: If you are unable to find superfine sugar, you can make it by placing granulated sugar in a food processor and pulse blending to desired consistency.