Break the chocolate into pieces, put into a small saucepan with water or black coffee and stir continuously over gentle heat until melted and thick and creamy. Remove from heat and stir in the butter and flavoring. Separate the eggs, putting the whites into a small bowl and dropping the yolks, one at a time,into the chocolate pan; stir well after each addition.NOTE:The chocolate should be hot enough so that when the yolks are added, they cook slightly.

Beat the whites until they hold a soft peak and fold very carefully into the chocolate. When thoroughly mixed, pour mousse into the pots and chill overnight in the refrigerator. For easy pouring, transfer first into a pitcher, scraping the pan with a rubber spatula.