Make cake mix as directed. Stir in chocolate chips and bake as directed in 9 X 13 pan in 350 oven. Cool 1/2 hour. Then poke holes in cake using the round end of a wooden spoon and pour the condensed milk all over it. Try to put into every hole. Refrigerate at least 2 hours. Frost with Cool Whip and then crumble candy bars on top. Frozen candy bars are really easy to work with. You can also buy Heath Candy bits, too.

fudge topping over cake, then finish up w/the Cool Whip and candy bits.

I've also served the cake while it's still warm. Either way, it disappears fast!