Leeks are mild members of the onion family. They have long thick white bodies with tough outer green leaves. They retain a great deal of dirt and must be washed thoroughly before using. They are split down the middle and rinsed under running water. Leeks are often used in soups and stews and prized for their mild flavor. In Korean cooking, raw leeks are cut into very fine thin matchstick strips and used as a condiment with certain dishes. When cooking with leeks, remove the outermost green leaves. If you are using leeks raw, remove all the green leaves, which are tougher than the inner white body.