The leek, a member of the onion family, is comprised of a mass of leaves, white and tightly furled in concentric rings in the lower portion and green, splayed and with a v-shaped cross-section above. This half-blanched appearance is not entirely natural and results from the practice of planting leek seedlings at the bottom of a cylindrical hole to keep the lower section out of the light. The white portion can be made even longer by subsequently earthing up each plant, and leeks of truly gargantuan size can be grown if you're so inclined.
Allium porrum as we know it today was first grown by the ancient Egyptians who are thought to have developed thicker-stemmed varieties from the even more ancient middle-eastern leek. According to the book of Numbers during their escape across the desert the Hebrews grumbled about only having manna to eat, recalling the leeks of Egypt with great fondness. The ancient Greeks and Romans also embraced the vegetable, the latter developing a belief that eating leeks imbues the voice with greater resonance and depth. The famously vain Emperor Nero had leek soup every day to improve his singing and oration, and was consequently nicknamed Porrophagus, 'leek-eater'.
It is widely believed that the Romans brought the leek to Britain, where as luck would have it the climate is ideally suited to its cultivation. Its adoption as a national symbol of Wales is said to have come from the Battle of Heathfield in 633AD where the Welsh combatants distinguished themselves from their Saxon opponents by pinning leeks to their headgear.
The long chain carbohydrates formed by heating give cooked leeks a slightly slippery feel which provides an unmissable opportunity to use the word 'mucilaginous'. It's the thickening quality associated with these carbs which makes the leek so well suited to use in soups and stews.
Varieties
As with many vegetables, planting early and late varieties lengthens the harvest. Carlton (early), Musselburgh (late) and King Richard (for early, baby leeks) have good reputations. It's a good idea to leave a few to go to seed for the following year. For more information on growing leeks, see here.
How to buy / what to look for
A good leek is not more than about an inch in diameter, smooth and perky. Leeks of prizewinning magnitude are impressive but invariably tough and woody. Don't worry about rusty orange or brown blotches on the leaves, but do buy more than you think you'll need to allow for losses caused by trimming.
Nutrition
Useful quantities of potassium, folic acid, vitamin C, iron and fibre. The green parts also contain beta-carotene.
Harvested
September - May
Storage
Leeks will keep in the fridge or another cool, dark place for about four days
Preparation and basic cooking
To prepare, remove any tired outer leaves and trim off about two-thirds of the remaining green matter and the roots. Split the leek lengthways starting a couple of inches from the root end, rotate 90 degrees and split again allowing the leaves to be splayed out and any soil between the layers to be rinsed out. Chop and steam or sauté in butter for about 5 minutes. The white part is that most often called for in recipes, but don't discard the green bits - use them in stock.
Goes with / good in
With potato in soups like vichyssoise and cock-a-leekie, as a side dish with fish, and in stews.
Recipes
Yotam Ottolenghi's fried rice cakes with creamed leeks and egg
Allegra McEvedy's gammon, leek and barley hotpot
Yotam Ottolenghi's leeks fried in breadcrumbs with crème fraîche and sweet pepper