My husband's mother used to roast a pork roast on top of a mac and cheese casserole. Of course, the first I heard of it was after she passed away. He and his sister remember it fondly but we haven't been able to replicate this. Apparently, she fixed it frequently when they were kids in the 50's. I am assuming it came from her family so I am guessing it might be a German tradition but I am not sure.