Leeks look like giant scallions and are related to both garlic and onions. Rather than forming a tight bulb such as the onion, the leek produces a long cylinder of bundled leaf sheaths which are generally blanched by pushing soil around them (trenching). They are often sold as small seedlings in flats which are begun early in greenhouses, to be set out as weather permits. Once established in the garden, leeks are hardy; many varieties can be left in the ground during the winter to be harvested as needed.
The edible portions are the white onion base and light green stalk. They are an essential ingredient of Cock-a-Leekie Soup and of vichyssoise. They can also be used raw in salads, doing especially well when they are the prime ingredient. Leeks make excellent side dishes and appetizers but can also be added to many entrees including soups, stews, quiches, and salads.
Because of their symbolism in Wales, leeks have come to be used extensively in that country's cuisine.
Leeks are found in markets year round with a peak during fall to early spring. Select leeks with clean white bottoms making sure that the ends are straight and not larger than 1 ½ inches in diameter, otherwise they will have a tough texture. The tops should be green, crisp and fresh-looking. Small to medium leeks (less than 1½ inches in diameter) are the tenderest.
Refrigerate leeks, unwashed, in a loosely fitting plastic bag for up to one week. Storing leeks in plastic helps them hold onto moisture and keep the odor from spreading to other foods.
Leeks carry some dirt especially in between the layer of overlapping leaves. Begin cleaning by removing discolored leaves and trimming off green tops and root tips. Cut the leek lengthwise by inserting a knife from the base. Spread the leaves and rinse thoroughly. Placing the fanned out leaves in a bowl of water and gently moving the leaves will loosen any remaining dirt.
This delicate vegetable cooks quickly and overcooking them will result in a slimy and soft product. In addition, they store heat well and will continue to cook even after the heat source is removed.