Bake cake in a 9x13'' pan according to recipe directions. Allow cake to cool for a few minutes, then poke holes in it with a fork or wooden skewer.

Pour caramel sauce and sweetened condensed milk all over the top of the cake. Set aside to cool completely.

Topping: Add the peanut butter and powdered sugar to a mixing bowl and mix until smooth. While mixing, slowly pour in whipping cream. Whip until stiff peaks form, and it hold its shape.

Finish: Spread the peanut butter whipped cream over the cooled cake and sprinkle crushed butterfingers on top. Refrigerate for at least 1 hour, or up to one day, before serving.