When I was a kid my mom would make potato pancakes with leftover mashed potatoes. I would put ketchup on those. outstanding!
I have not had those in years but I did the same. Like french fries. My mom use to cut up potatoes in cubes and fry them in real butter. I loved them and put catsup on them. Years later when I made them, I would add a cut up onion. I made some recently and they were so good. I do not cook much since it is just me. I like some brands of frozen meals. God bless.