Butterfinger Cake

2 angel food cakes
4 egg yolks
3/4 cup butter
2 cups confectioners' sugar
1 (16 ounce) container Cool Whip
7 Butterfinger candy bars, frozen and crushed

Mix together eggs, sugar, butter and Cool Whip. Crumble up 1 cake and combine with 1/2 of the Cool Whip mixture in a 13 x 9-inch pan. Sprinkle 1/2 of crushed candy bars on top. Repeat process with remaining ingredients, layering on top of first. Chill for at least 3 hours, then serve.