Leeks, along with onions, garlic and shallots, belong to the allium family of vegetables. Rather than being squat and bulbous, though, they resemble spring onions on steroids. In Cantonese, they're called dai chong (big spring onion).
Leeks are much more expensive than other allium vegetables and a lot of each specimen goes to waste. Only the bottom part of the leek, which is white and pale green, is tender enough to eat; the dark tops can be used to flavour stocks and sauces. Buy leeks that are firm and glossy. Peel away any shrivelled layers until fresh, smooth ones are revealed. The layers can hide a lot of soil, so they need to be washed well. The easiest way to do so is cut off the stem and slice it lengthwise before rinsing.
When sliced, leeks release the same sulphurous compounds that cause eyes to water when we chop onions, garlic and shallots, although they're not nearly as strong. Raw leeks have a milder flavour than other allium vegetables and become sweeter with cooking.
For a simple dish that showcases the vegetable's taste, cut and wash the leeks then chop into fine semi-circles. Melt some butter in a skillet, add the leek and season with salt and pepper. Stir to coat with the fat and add a splash of unsalted chicken stock. Cover the pan with a lid and simmer over a low heat until the leek is very tender. Serve with mashed potato and a seared, skin-on salmon fillet.
