Peel potatoes and cut them into large, even-sized pieces. Place potatoes in a large, heavy pot, cover them by at least a couple of inches with water and add a small fistful of salt. Bring to boil over medium-high heat. Boil the potatoes until they're very tender, 12-16 minutes.

Meanwhile, heat the milk (or half-and-half, or buttermilk) and butter in the microwave oven or in small pot on the stove. Keep the mixture warm. When potatoes are tender, drain off all the water and place the pot over a low flame. Shake the pot for a moment or two to dry the potatoes off completely. Pass potatoes through an old-fashioned hand-held potato ricer into a bowl, or mash them with a potato masher or electric beaters until no lumps remain. (Either way, take care not to overwork the potatoes, or their texture will turn gluey.) Use a rubber spatula to fold in the warm milk mixture, plus salt and pepper to taste.

Serve immediately, or let them stand for up to one hour then reheat gently in the microwave oven just before serving. Makes 6-7 servings.