Fresh wasabi was once served solely in high-end Japanese restaurants - in Hong Kong, anyway - and often, only if you asked for it; the chefs weren't going to waste the expensive ingredient on people who didn't know any better. Wasabi paste - the kind you squeeze out of a tube - and wasabi powder, which is mixed with water, couldn't be more different to fresh wasabi stem grated on a sharkskin grater. The colours are similar but, if you look closely, you'll notice fine shreds in the fresh wasabi.

Many people mistakenly believe that the sinus-clearing pungency of wasabi paste (served in mid-range restaurants) and wasabi powder (used at the cheapest places) is the flavour of ; a friend who has a Japanese restaurant says some of his customers complain that the freshly grated stuff he serves has no flavour. , in fact, is much more subtle; it has a mild pungency and gentle heat. The powder and paste are actually made from a plant from the same family as wasabi: horseradish, which is much larger, with a stronger, more fiery taste.

One of the reasons is expensive is that it is hard to grow: it needs clean, running water. The plant is believed to have myriad medical uses - it has anti-inflammatory properties and is said to strengthen the immune system, alleviate arthritis and even cure certain types of cancer.