Toffee Cake
["1 box devils food cake mix", "1/2 (14-oz) can sweetened condensed milk", "6-oz caramel ice cream topping", "3 (1.4-oz) bars chocolate covered toffee, chopped", "8-oz Cool Whip"]
["Bake cake according to package directions in a 9 x 13 pan. Cool on wire rack for 5 minutes. Make slits across the top of the cake, making sure not to go through to the bottom."]
["cake mix", "condensed milk", "caramel ice cream topping", "chocolate covered toffee"]