I have also been looking for a way to substitute the dry frosting mix for the recipe. I had made these cookies every Xmas and my mother used to make them for us, as well. For awhile there was a German chocolate brownie mix. In it was a packet of dry frosting mix that I used to use. It worked well. Now I can't find that brownie mix being made anymore. If you figure anything out, would you let me know?
Good luck to both of us!!