creamy as mayonaise. In a heavy 4 to 6 cup saucepan, melt the chocolate with the coffee over hot water, stirring constantly. When all of the chocolate has dissolved, beat in the butter--one piece at a time--to make a smooth cream. Then beat the chocolate mixture into the egg yolks and sugar. In a seperate bowl, with a clean whisk or beater, beat the egg whites until they are stiff enough to form stiff peaks on the wires of the whisk. Stir about quarter of the egg whites into the chocolate mixture to lighten it, then very gently fold in the remaining egg whites. Spoon the mousse into the oiled mold or dessert cups and refrigerate for at least four hours or until it has set. To unmold and serve, run a long sharp knife around the sides of the mold and dip the bottom of it in hot water for a few seconds. Then wipe the outside of the mold dry, place a chilled serving plate upside down over the mold and, grasping both sides firmly, quickly turn the plate and mold over. Rap the plate on a table and the mousse should slide easily out of the mold. If the mousse doesn't unmold at once, repeat the whole process. With a wire whisk, rotary or electric beater, whip the chilled cream in a large chilled bowl until it is firm enough to hold its shape softly. Garnish the mousse with the whipped cream.