IT MAY BE hard to accept that something that looks so gnarled and dirty, grows five to 10cm underground at the base of trees and has to be rooted out by pigs and dogs could be a delicacy. Yet for centuries the truffle has been celebrated as 'the diamond of the kitchen', feted alongside such extravagances as caviar and foie gras, because it has a taste and smell most people find delicious yet difficult to describe. And it's scarce. Although truffles can be found in China, Australia, New Zealand, Spain and Sweden, experts say premium truffles come only from France and Italy. The black truffle (Tuber melanosporum) is most famously grown in the Perigord and Lot regions of France. Others say that the white truffle (Tuber magnatum), which hails from Piedmont and Umbria in northern Italy, is superior. The truffle season for both varieties runs from late autumn to winter. Truffles have an unusual taste and aroma. Even asking experienced French and Italian chefs to describe it typically produces a hushed silence as they struggle to put the sensations into words.'The smell is just amazing,' says Didier Rochat, executive chef of Central restaurant Cafe des Artistes, after a considered pause. 'It's so strong, it drives you crazy when you open the box. When you know them and work with them, you want them all the time, but unfortunately they're seasonal.' Gary Cheuk Shiu-kuen, chef de cuisine at French restaurant one-thirtyone in Sai Kung, says customers tend to love or hate them. 'If people don't like them they say they smell like gas,' he says with a laugh. 'But I love them.' Cheuk's signature truffle dishes include homemade foie gras terrine with layers of black truffle and confit de canard with black truffle layers served with homemade brioche toast. Black truffles are said to be more pungent, with an earthy, almost fetid, smell. Perhaps it's this earthiness that's given them the reputation as an aphrodisiac. Sergio Zanetti, chef de cuisine at the Mistral Italian restaurant at the InterContinental Grand Stanford in Tsim Sha Tsui, is a native of Piedmont. He describes the taste as 'similar to artichoke and garlic'. Zanetti's favourite truffle dishes take account of the delicacy of white truffles, which are usually shaved onto dishes such as salads or over pasta and risotto just before they're served. 'You don't need to cook white truffles because they're rich in oil,' he says. 'If you cook them, the oil evaporates and you lose the flavour.' There's another reason truffles are served in small pieces or shaved: they're expensive. Black truffles can fetch up to $25,000 a kilogram, and the white variety sometimes sell for more than $35,000. The price depends on their size and how many are found each season. Of late, the price has been rising because it's hard to cultivate truffles, and the areas where they grow have steadily been encroached on by developers. As well, the demand is rising. 'In my opinion it's the rarity [that makes truffles so sought after],' says Cheuk. 'You only get them for a maximum of three months a year. It's like the Chinese summer yellow roe crab, which comes out only in the hottest months.' Truffles are also highly perishable. Massimo Iarossi, head chef of the recently opened Angelini Italian restaurant in the Kowloon Shangri-La, says that imported truffles sometimes last no longer than a week. 'Sometimes it's difficult to convince people to spend a lot of money to try just a few slices,' he says. 'Sometimes people expect much more than what they get. It's a challenge to educate people.' Iarossi's truffle dishes include beef tenderloin carpaccio with wild rocket and parmigiano flakes, smoked cheese risotto, and pan-fried veal fillet with a porcini mushroom sauce. He enthuses about the flavour that just a few truffle shavings can add to a dish. 'It's like walking in a forest in the northern part of Italy in the autumn,' says the Piedmontese. 'There's the smell of mushrooms and it's like a wooden flavour in the air.' Given the exclusivity and expense of European truffles, Chinese alternatives have begun encroaching on the market, as have those from Australia (where there are more than 250 varieties) and New Zealand. But the flavours of the French and Italian black and white truffles are so distinctive that these others are seen as inferior. 'They're not the same as the European ones,' says Cheuk of the Chinese variety. 'Truffles depend on the soil, climate and water, and the real black truffles aren't easy to grow. Truffles are like gold.'