LEEKS
Leeks have a more delicate flavor than onions, although they still belong to the same family that also includes garlic, shallots and scallions. Leeks, or Allium porrum, have a long cylindrical stalk that grows in diameter as the leek ages. The stalk is composed of concetric layers of leaves that usually have to be washed before using. There is also a wild variant of leeks that is smaller and much more intensive in flavor.
The history of leeks in cooking spans many ages, and they are very popular in northern Europe where they were brought to by the ancient Roman empire. They are so popular indeed that Wales have put them into their national emblem (this relates to a successful battle against the Saxons in 1620). Leeks have also been used in medicine as they were esteemed for their benefits to the throat. Even some singers ate leeks supposedly to improve their voice.
When buying leeks, choose the ones that are firm (not slimy), have fresh-looking leaves without any cracks or discolored spots. They should be green and white. Also, pick the leeks that are fairly small, as the bigger leeks have already started to develop a wooden texture in their middle part. You can feel the leek at its root, where the hairy part is - feel with the finger at the underside of the root if the middle feels wooden or not. When you have bought the leeks, wrap them loosely in a plastc foil and put them in the refrigerator. Leeks are best in the beginning of the spring, but they can be eaten basically all year round as they can withstand cold climate.
Leeks have most taste in the innermost leaves. The outermost part of the green part at the end of the leek taste more like cabbage than like an onion, and so it is usually discarded. The root of the leek is also discarded.
When cooking leeks, the outermost leaves are usually removed (can be used in stocks; otherwise discard them). The outer part of the green leaves arer cut off and discarded. Then, a long cut is made that runs through the middle of the leek, so that the separate leaves can be rinsed with water. Be sure to remove all sand and stones. Then the leek may be prepared in a way that is desired. Cooking leeks should be done with care as they become "slimy" and mushy when overcooked. Cooked leeks are not very sustainable in a refrigerator, a couple of days at best. Leeks can of course be frozen but they will lose their flavor and texture.
Leeks can be eaten raw as well - they make an interesting addition to some salads - although they are most often used as cooked or sautéed. A popular leek-oriented dish is a nice cold soup called vichyssoise. Leeks can also be used in bouquet garni, as a basic ingredient in stocks and soups, or as a component of a veggie mix that is served along with meat or fish.
From the health point of view, leeks contain a lot of vitamin C, iron, and some B vitamins. They also have a good amount of dietary fibers. Leeks, as well as other onion family vegetables, are known to lower the bad cholesterol levels in the blood. They are also considered to reduce the risk of getting colorectal cancer. Some concern with leeks is the relatively high amount of oxalates that can be troublesome for people with tendencies for getting kidney stones, since oxalates are a common cause of this disorder.