Leeks will not form bulbs or produce cloves like their cousins, but instead develop an edible, 6–10 inch-long, round stem that can measure 2 inches in diameter. The leek's cylindrical, white, edible root gradually becomes a stalk with a fan of dark green, flat leaves. Offering an earthy, mild onion flavor, the texture of a leek is crunchy when raw and silky when cooked. Leeks are considered to be the sweetest and most mild members of the onion family.
Leeks are a good source of iron, vitamin C, and folate. Four ounces of raw leeks contain about 75 calories.
Though leeks are often interchangeable with onions and garlic, they can require specific preparation and are often highlighted in recipes for their particular flavor. Slowly cook sliced leeks in olive oil and butter until soft, then toss with beans and pasta. Cook with potatoes and vegetable broth, the puree for a classic potato-leek soup. Slowly cook with butter and cream and serve with seafood such as seared scallops. Grill whole or halved leeks as an appetizer or as a topping for bruschette. Braise until very tender in wine and vegetable stalk, then top with a mustard-based vinaigrette. Add sauteed leeks to quiche, savory tarts, or pies. Refrigerate for up to three days in a plastic bag.
Leeks are available year-round, with a peak season in late winter or early spring.