1 Preheat oven to 350 degrees F (175 degrees C). Grease and flour three 8 inch round cake pans.
2 Prepare cake mix according to package directions. Pour batter into the prepared pans.
3 Bake at 350 degrees F (175 degrees C) for 30 minutes. Let cake cool slightly then pierce cakes with a fork. Pour the coffee liqueur gradually over the three cake layers.
4 Prepare the chocolate mousse according to the package directions. Let chill in the refrigerator.
5 Once cake is cool break it into pieces. Layer cake pieces, chocolate mousse, crushed butter toffee candy bars, and whipped topping 1/3 at a time in a large glass bowl. Grate the chocolate candy bar over the top. Let chill in refrigerator for several hours before serving.