Slow Cooker Hot Fudge Sundae Cake Awesome cake! I not only doubled the recipe, but I mixed everything together instead of leaving the sauce on top. The result was a chocolate cake with fudge sauce rippled throughout. Some reviews on here were not in favor of using the walnuts, but I felt they were a positive addition to this recipe. The next time I fix this, I will put the fudge sauce in the cake, as well as on top of it.