Spring onions play a prominent role in Asian cuisines. The long, slender immature onions are also known as green onions or scallions, although scallions are larger, sweeter and milder.
Despite their name, spring onions are available year-round. Look for pliable, slightly moist onions that are firm at the base. If the only ones available look dried out, you can usually peel away the outer layers to get to the moist interior. Although many people only use the white and pale green base of the spring onion, the entire stem is edible. Sometimes the onion can have a purplish base but there doesn't seem to be any difference in flavour. Spring onions are often given away for free at the wet market when buying vegetables - the vendor will ask if you want 'choong' and will slip a few into the plastic bag along with the vegetables.
Spring onions are used extensively in Chinese cooking as flavouring, a garnish or a vegetable. To make the spring onion 'brushes' often served with Peking duck, trim off the ends of the spring onions then cut the white and pale green parts of the stem into five-centimetre lengths. Use a sharp paring knife to cut the ends of each piece into a fine julienne, cutting lengths only 2cm down each end and leaving the 1cm in the middle intact. Put the lengths of spring onion in ice water and the ends will curl.
The spring onion dipping sauce commonly served with baak chik gai (white cut chicken) is easy to make and delicious. Chop some spring onions finely then mix with salt, to taste, and enough vegetable oil to form a loose paste. You can also add a few drops of sesame oil.
For a good northern China-style dish in which spring onions are used as a vegetable, marinate thin slivers of lamb in soy sauce, rice wine, oil, sugar, salt, ground pepper and cornstarch. Cut lots of spring onions into 4cm lengths. Heat some oil in a wok and fry a couple of slices of ginger and one or two cloves of garlic until they are fragrant. Add the spring onions and fry them quickly so the exteriors are shrivelled but the onions are still firm, then remove from the pan. Heat more oil and cook the lamb until it loses its pink colour, then return the spring onions to the pan and cook to blend the flavours. Taste for seasoning (it's good with a lot of pepper) then drizzle with sesame oil. This is good over rice, but even better when stuffed into zhao beng - the sesame seed 'pockets' that are a speciality of Beijing cuisine.