I just read this in Cook's Country magazine. This cake was all the rage when I was a little girl. Pillsury discontinued the "secret ingredient" which was a Double Dutch Fudge frosting mix. The writer of this article reworked the recipe, (2 dozen times!) until she came up with this, which she says is just like the 1966 Bake-Off winner, with the fudgy "tunnel" frosting-like filling that holds its shape when cut. I'm saving it here to try! Cooking time includes required cooling time.