Scrub the potatoes and boil them in their jackets. Finely chop the scallions. Cover the scallions with cold milk and bring slowly to a boil. Simmer for about 3 to 4 minutes, then turn off the heat and leave to infuse. Peel and mash the freshly boiled potatoes and, while hot, mix with the boiling milk and scallions. Beat in some of the butter. Season to taste with salt and freshly ground pepper. Serve in one large or four individual bowls with a knob of butter melting in the center. Champ may be put aside and reheated later in a moderate oven at 350°F. Cover with foil while it reheats so that it doesn`t get a skin. Add 2 to 3 tablespoons of freshly chopped parsley to the milk, bring to a boil for 2 or 3 minutes only, to preserve the fresh taste and color. Beat into the mashed potatoes and serve hot. Substitute freshly chopped chives for parsley. Soak a couple of fists of seaweed in cold water for an hour or more. Drain and stew in milk until tender, about 3 hours. Add a good knob of butter and some pepper and beat into the mashed potato. Taste and correct the seasoning. Serve hot. This special champ could only be made for a few weeks when the fresh green peas were in season. Cook the peas in the boiling salted milk with a pinch of sugar until tender. Add to the mashed potatoes and pound together in the usual way.