combine the chocolate,butter,and coffee in the top of a double boiler over hot,but not simmering water,strring frequently until smooth.Remove from the heat and let it cool
Once the melted chocolate is cooled slightly whip the eggs in a medium bowl until they are foamy and begining to hold a shape.Sprinkle the sugar and beat
When the chocolate had reached to its proper consistency stir it into the yolks.Gently stir the whipped cream.Fold in half the white just until incorporated,then fold in the remaining white, and finally the remaining white cream.
Spoon or pipe the mousse into a serving bowl. Refrigerate upto 8hours or upto the day