Champ is a traditional Irish mashed potato side dish. It is served piping hot in mounds on plates. You make a hollow in the centre of your mound of champ, and place a big gob of butter in that hollow where it will melt. You eat champ from the outside of the mound in, dipping each forkful into the pool of melted butter. This dish is very similar to Colcannon.
Peel potatoes, boil in salted water until tender (about 35 minutes.)
Meanwhile, chop the green onions, add to the milk in a saucepan and bring just to a boil, then reduce heat and simmer for about 7 minutes, then remove from heat and set aside.
When potatoes are done, mash them, then add the butter, the milk and green onion mixture, and season with salt and pepper. Serve hot.
The Irish will sometimes use young nettles or scallions instead of green onions.