1 big fat leek, or 2 slightly slimmer ones
1 smallish onion
2 small-to-medium new potatoes
1 tablespoon butter
3 cups water or more
Salt, fresh ground pepper
1-2 tablespoons heavy cream, optional
Trim the leeks, discarding the tough green tops, and cut them into 1-inch chunks.
Rinse thoroughly and drain. Peel and chop the onion and potatoes.
Melt the butter in a heavy pot and saute the onion for a few minutes.
Add the leeks and potatoes and sweat them over low heat for another few minutes, stirring frequently.
Add the water and a pinch of salt, and bring to a boil.
Cook at a lively simmer, with cover askew, for 1 hour, until the potatoes are velvety soft.
Now mash roughly with a potato masher or slotted spoon.
Add considerably more salt to taste, and a few grindings of the pepper mill. Serve as is, or swirl some cream on top.
Source: Judith Jones, “The Pleasures of Cooking for One” (Alfred A. Knopf, 2009)