Unlike its allium cousins—garlic, scallions, and onions—which you can eat raw, a leek must be cooked thoroughly or you’ll have a tough, stringy result. Leeks grow in sandy soil and need thorough washing to get rid of the grit. Look for firm, green stalks with the roots still attached.
To cook, trim the root and dark green parts (but do save both for vegetable stock). Chop leeks and sauté them with carrots and celery for the flavorful start to a braise, a stuffing, or a stew. Sweat them to purée for leek and potato soup. (Know that the sugars in leeks make them prone to sticking in the sauté pan if you don’t use enough oil). Simmer whole leeks in chicken stock for a delicious side dish, served warm with a few grinds of black pepper or cold with a vinaigrette.