Leeks are a milder cousin of the onion. They resemble the smaller green onion, with long leaves on top and short roots on the bottom. In short, the white and light green parts of the leek are edible, but cooking with leeks takes some preparation.
Selecting the freshest leeks ensures the best-tasting dishes. Choose small to medium-size leeks with long, white stalks. The dark green leaves should be firm, crisp and free of spots or blemishes, and a small amount of hairy roots should remain. Avoid yellowed or dry roots and wilted leaves and stalks. Like many root vegetables, leeks thrive in cooler temperatures. Peak season for leeks is September through December.
The tender, light green and white parts of the leek are used for cooking. The dark green leaves are tough and should be discarded. Before washing, remove the roots as well. Because leeks are root vegetables that grow largely underground, they often come to you with a fair amount of grit in the leaves. They must be rinsed thoroughly to remove the sand. If the recipe calls for whole leeks (e.g., braised leeks), run the leeks under cold water, gently separating the leaves with your hands. For a more thorough cleaning, cut the leek in half lengthwise. Rinse them for several minutes to be sure all the grit is removed. If the recipe calls for sliced leeks (e.g., potato leek soup), slice the leeks to the desired thickness. Fill a large, deep bowl with cold water and submerge the sliced leeks. Stir the leeks with your hands in the bowl, allowing the grit to fall to the bottom. Remove the leeks and pat dry. If you do not plan to use the leeks immediately, refrigerate them in a plastic bag for up to five days.
Cooking with Leeks
Leeks are a mild onion with a subtle, garlic-like flavor. Unlike green onions, they are not often eaten raw. When cooked, leeks are a healthful addition to any recipe that calls for onions or as a vegetable side dish or entrée.
Classic Leek Dishes
Potato leek soup is a classic dish of cream, potatoes and garlicky leeks. In a large saucepan, melt 3 tbsp. of unsalted butter. Add 1 lb. of sliced leeks and sweat them with a pinch of salt over medium heat. Reduce the heat to medium-low and cook until the leeks are tender, about 25 minutes. Add three small, diced Yukon Gold potatoes and 1 qt. of vegetable broth and bring to a boil. Reduce the heat to low, cover and simmer for about 45 minutes. When the potatoes are tender, turn off the heat. Puree the soup with an immersion blender, or carefully transfer to a blender in batches. Stir in 1 cup each of heavy cream and buttermilk and salt and pepper to taste. Garnish with fresh chives. Braised leeks are a sophisticated vegetable side dish. Leeks are halved and cooked slowly in a flavorful broth. Remove the green leaves and the hairy roots of four to six medium-size leeks, leaving the bottom of the leeks intact. Halve them lengthwise so the leaves stay together, and rinse the leeks thoroughly. Melt 3 tbsp. to 4 tbsp. of butter in a large sauté pan over medium-high heat until it foams and reduce heat to medium. Add one minced garlic clove and the leeks, sliced-side down in a single layer. Brown for one to two minutes on each side, sprinkling with salt. Return the cut side down, sprinkle with 1 tsp. of sugar and 2 tsp. of thyme, and add 1 cup of white wine or vegetable stock and a bay leaf. Bring to a simmer, cover and cook for 35 to 45 minutes over medium-low heat. When the leeks are tender, remove the lid and bring the broth to a boil until reduced by half. Garnish with fresh parsley.