In the days before agriculture became a multinational industry, when people ate fresh produce according to the seasons, spring onions were available primarily - as the name suggests - in the spring. Seeds were scattered and when they started to sprout, some of the immature onions were pulled out to leave room for the others to grow. The long, slender onion, which is white- to-purple at the tip with a pale green midsection and a hollow, dark green top, is now grown for its own sake, rather than as a by-product of the bulb onion. Called various names, including green onion, scallion and chong (in Cantonese), there are many varieties of spring onion, although it would take the sharp eyes of a botanist to tell the difference between some. In general, the more slender an onion is, the milder it will taste. Many recipes use only the white to pale green part of the vegetable, more for aesthetic reasons than any other. The entire onion is edible (although the roots are almost always discarded) but the darker green ends are slightly tougher. Spring onions should be firm and moist, rather than limp. If they're slightly past their prime, you can strip off the dry, outside layers to reveal the fresh interior. They should be stored in the fridge wrapped in a plastic bag or cling-film (to prevent them drying out). Spring onions are an important part of many Asian cuisines because they're much milder than bulb onions. They're such an integral part of Cantonese-style steamed fish (because the vegetable counteracts the 'fishiness') that if you buy a fresh fish from a wet market, the vendor will often add a few spring onions (along with some fresh coriander) to the bag. The cleaned fish should be slashed and rubbed with a little rice wine. Put a whole spring onion and some julienned ginger in the cavity and put it in a heat-proof shallow dish. Scatter more julienned ginger over the fish and drizzle with soy sauce. While the fish is steaming, heat about 30ml of cooking oil until it's very hot. When the fish is done, cover it with a pile of fresh coriander and shredded spring onion and drizzle the hot oil over the top. For a tasty dipping sauce for poached chicken, finely mince some spring onion then mix to taste with fine salt and cooking oil. Or, for an accompaniment to barbecued meat, finely shred some spring onion and mix it with small lettuce leaves, salt, sesame oil and Korean chilli flakes.