Death by Chocolate

1 box chocolate cake mix
1 cup Kahl?a liqueur
3 (5 ounce) boxes Jell-O? chocolate mousse
3 (8 ounce) containers Cool Whip?
6 Heath? bars, crushed

Bake the cake as directed in a 13 x 9-inch pan. Let the cake cool, then poke it with a fork all over. Pour Kahl?a over the cake and refrigerate overnight or several hours. Make the mousse as per package directions and layer it with the Cool Whip? and crushed Heath? bars.