The Leek (puerro) is a vegetable that belongs, along with onion and garlic, to the genus Allium. The edible part of the leek plant is a bundle of leaf sheaths that is sometimes erroneously called a stem or stalk.
Leeks are easy to grow from seed and usually reach maturity in the autumn months. They have few pest or disease problems. Rather than forming a tight bulb like the onion, the Leek produces a long cylinder of bundled leaf sheaths that are generally blanched by pushing soil around them (trenching). Once established, Leeks are quite hardy and many varieties can be left in the ground during the winter to be harvested as needed.
Leeks have a mild onion-like taste and in its raw state, the vegetable is crunchy and firm. The edible portions of the Leek are the white base of the leaves (above the roots and stem base), the light green parts and to a lesser extent the dark green parts of the leaves. Thorough washing is very important for Leeks, as soil is often trapped between the many layers of leaves. One of the most popular uses for Leeks is for adding flavour to stock. The dark green portion is usually discarded because it has a tough texture, but it can be sautéed. Leeks are usually chopped into slices 5-10mm thick and the slices have a tendency to fall apart, due to the layered structure of the Leek. They can be boiled, which turns it soft and mild in taste, or fried, which leaves it crunchier and preserves the taste. They can also be eaten raw in salads, especially as the prime ingredient.
Leeks are used in many cuisines, including Turkish cuisine when they are chopped into thick slices, then boiled and separated into leaves and finally filled with a filling of rice, herbs (generally parsley and dill), onion and black pepper. Olive oil, currants, pine nuts and cinnamon and meat can also be added to the mixture. Leeks are an ingredient of Cock-A-Leekie Soup, Leek and Potato Soup, and Vichyssoise, as well as plain Leek Soup.
Because Leeks are the national symbol in Wales they have come to be used extensively in that country’s cuisine. According to one legend, King Cadwaladr of Gwynedd ordered his soldiers to identify themselves by wearing Leeks on their helmets in an ancient battle against the Saxons that took place in a Leek field. Perhaps the most visible use of the Leek, however, is as the cap badge of the Welsh Guards. Elsewhere in Britain, Leeks have come back into favour over the last 50 years. The Leek was the favourite vegetable of Emperor Nero, who consumed it in soup or in oil, believing it beneficial to the quality of his voice.