As I know them, champ and colcannon are pretty much the same thing. The key ingredient to both of them, though, is GREENS - whether they be scallions, kale, finely shredded cabbage or (your choice here). Onions are a good addition. Cheese? Could work, but that's not what makes it champ. Oh, and lots of butter. Champ is definately more on the oozy, liquidy side than regular mashed potatoes.