Barely melt the chocolate in a double boiler over gentle heat. Remove from the heat source and pour into a large mixing bowl then cool for five minutes. Add the butter, cream, vanilla, coffee-flavored liqueur, and mix on medium speed until the mixture thickens. Finally add the confectioners' sugar in small batches until the mixture holds a medium peak. If the kitchen temperature is warm, and the icing is not of spreading consistency place the bowl in the refrigerator for a few minutes, then recommence mixing. Slather the icing over the cake with an offset palette knife.