Butterfinger Cake
["1 box Duncan Hines yellow butter cake mix", "8 Butterfinger bars, crushed", "16 oz. Cool Whip", "1/2 c. margarine, melted", "2 egg yolks", "2 c. powdered sugar"]
["Cook cake per mix directions."]
["cake mix", "Butterfinger", "margarine", "egg yolks", "powdered sugar"]