Has there been a better assignment in the history of OFM? I'm sitting over coffee in the Ritz-Carlton hotel in Hong Kong, making a plan with Alan Yau to eat our way across the cradle of Cantonese cuisine. You could not really pick a better guide. Yau is one of world cuisine's great mediators, a man who brokers new deals between the fusion-overdosed West and real far-Oriental food. He was the brain behind Wagamama, the chain of noodle canteens where the British learnt to share tables and slurp like the Japanese. Revolutionary stuff, in 1992. (Now, in the tradition of most great, simple catering ideas, Wagamama is a 26-strong national restaurant operation with franchises across the world. It changed hands for £60m last summer.)

Yau's Busaba Eathai restaurants have moved the much-abused Thai cuisine away from over-priced, over-spiced green and red curries. In 2001 he raided his Hong Kong roots - he was born in 1962 in a town on the Chinese border - and opened Hakkasan, Britain's first Michelin-starred Cantonese. At his latest London restaurant, Yauatcha, Yau has overturned one of Chinese-grub etiquette's most annoying rules: he lets you eat dim sum in the evening. So, as we get up to begin our eatathon, I think smugly about all the people I know who would cut off their right arm and barbecue it, cha siu-style, to be me today.

In the Ritz-Carlton lobby, a TV chef with lacquered hair pats Yau for 'pushing the agenda' on one hot topic: the great Chinese pudding problem. Yau has spent the past few days judging Hong Kong's 'Best of the Best' food Oscars. Last night's prize-giving controversy is still raging.

At the judging, Yau had said there shouldn't be an award for desserts if it was to go to someone making the sugar-loaded fancies that pass for Chinese pud. The problem, Yau explains, is symptomatic of Hong Kong cuisine. 'There's no innovation and that's because there's no dessert tradition. In Chinese restaurants they come out of the dim sum kitchen. Hakkasan's are done by a team of Italian guys. It's going to take a long time to move the agenda on.'

But doesn't Hakkasan do a great mango spring roll? 'I took it off,' says Yau, severely. 'It was too cliched, superficial. Like strawberry sushi in a Japanese restaurant.'

While I wouldn't say no to a bit of strawberry sushi, I have a taste for Yau's puritanism, which is at the heart of what I think we're going to have to call his philosophy. 'I like to get into the deeper semantics of these things. I'm interested in using traditional ingredients - jasmine flower, chocolate fondant - in a modern way. But without the superficiality of just being shocking or contrary. Keeping it Chinese, not fusion, and still being modern - that's difficult.'

All this is as much on his mind as his other reason for being in Hong Kong - he is preparing to open a Hakkasan in his birthplace. The deal is nearly done and the opening should be by the end of 2005. It will be a big moment for the 42-year-old who grew up far from Hong Kong island's glitter, in the impoverished New Territories commuter town of Sha Tau Kok.

The restaurant will repeat the design concept of the London Hakkasan - perhaps the first Chinese restaurant in Britain, at least, ever to merit the word 'sexy'. (Its designer, Christian Liagre, set out to 'give the impression of descending to a decadent brothel in Shanghai'.) Yau says the look is a backlash against the minimalism that has dominated posh Asian restaurants in Europe and the US for so long: the curse of Zen. 'It's a shift back to what Chinese restaurants should be in terms of luxury, sensuality, mystery.' That will be a shock to Hong Kong, where restaurant style is chiefly red and gold gloss, strip-lit, and size is large-to-industrial. 'I'm not saying my restaurant will be better, but it will be different. There would be no point coming back here otherwise.

'Some things will be easier - the quality and variety of the ingredients available here. We're missing 30 per cent of what we need for the London restaurants because of European import controls. And here there's no lack of great chefs. The standard of Hong Kong cooking is phenomenal, but the restaurants are stuck in another age.'

Hong Kong critics have seen Hakkasan and Yauatcha in London, and given them the thumbs-up, if with less gush than their British counterparts. 'That's rewarding - Hong Kong critics are much more fussy. British critics look at the restaurant as a whole entity, the atmosphere, the service ...' (a sore point: The Times's critic loved the food but said the 'dopey' staff at Yauatcha made him consider sawing off his foot) ' ... but Hong Kong critics look at the food. Very seriously. They're more forgiving about service, but they're ruthless about what they put in their mouths.'

Our first restaurant, when we get to it, is neither minimalist nor industrial. The Tai Wing Wah, the Very Glorious Restaurant, is in a cluster of tatty concrete towers in the New Territories suburb of Yuen Long. It's a weekday morning and the elderly patrons are hard at work on dim sum and sponge cake. We're here to sample the 'village cuisine' of Hugo Man-To Leung, its chef-director's speciality. Fresh food, traditionally cooked and organic, is available according to the season. This is new for Hong Kong. It's the sort of venture that intrigues Yau, who saw his table-sharing, average £2-a-dish Wagamama as an experiment in sociopolitics as much as a restaurant.

Although it looks like a local diner, the rich from Hong Kong island have been flocking to Hugo's place. 'It's peasant food elevated to a level where the wealthy can come and eat across the class barrier, go back to a romanticised peasant past,' says Yau. Sort of like the River Cafe, then?

Hugo Man-To Leung is no Rose or Ruthie, though. He's a big, garrulous man, who immediately lays down a barrage of dishes at our table. His cha siu pork is unusually juicy, made using pieces from the front of the pig's neck, and the prawn-filled shu mai dumplings are excellent.

This is usual Cantonese fare - good quality, not extraordinary. But then we get to grips with a roast chicken, squeaky tender to the bite and sweet. Its secret is a 10-minute pre-oven soak in soy sauce, tangerine peel, cinnamon and aniseed. When I decide to impress the table by being the guy who eats the brain out of the chicken head that's peeking over the side of the dish, I'm told to put it down and behave. The head is not for eating: it's there to prove how fresh the bird is - look, says Yau, no hole in the neck. That means it's just been killed: it hasn't been hanging in a shop.

What gets all of us excited are the dipping sauces served with it. There's a 'homemade Worcester sauce', a chilli oil flavoured with olive leaves ('Incredible!' raves Yau); the best dip is yellowish and opaque, with coriander floating in it. The flavour is intensely salty and tangy: chopped ginger and the clarified fat of the chicken. 'Oh my God, this is incredible,' says Yau, and it is.

We ask for Hugo's formula. 'It's 40 per cent quality of the ingredients, 30 per cent quality of the cooking and 30 per cent quality of the soy sauce,' he says. Hugo makes his own 'virgin' soy sauce - taking only the product of the first fermentation. No one is ever going to successfully copy his dishes, he insists, because they'll never have his tofu. When Hugo's back is turned we admire the decor. 'Chinese restaurant designed by Quentin Tarantino,' says Yau. The room is a classic of haute chop-suey style: swirly carpet, gold wallpaper and a gallery of photos of Hugo beaming beside well-fed, C-list celebs. This is of interest to Yau, whose next London restaurant, DaiDaiYa ChowBar, will echo the dubious glories of the classic British chop suey house and 'Canton pop cookery'. 'Think Siouxsie and the Banshees meets Hong Kong Garden,' he says. 'But ChowBar won't be retro, because I don't want to return to that - it wasn't good - but a redefining of the cliche: we'll keep the chicken chow mein, but make it a modern version. It won't have Mateus Rosé and Blue Nun - that would be too Modern Chinky. But it will be a bit tongue-in-cheek ...' The designer of the Hotel Costes in Paris, Jacques Garcia, will be in charge of the look - the Middle Kingdom through Western imperialist eyes.

We leave for Tai Po, a nearby town with a famous food market. We're not far now from the village where Yau grew up. 'We came from a very poor background,' he says. The family were of the Hakka ethnic group, China's wanderers. Yau's father, Yau Cheung Wo, was a tailor who left for England when Yau was three years old, determined to work his family out of poverty. Yau's mother, Ting Fung, followed three years later, leaving the children to be brought up by their grandparents. Yau remembers his grandfather cooking Hakka food, typified as 'the very freshest vegetables, because we grew them, and hardly any meat, probably because we couldn't afford it'.

In 1975, aged 12, Yau and his younger brother and sisters went to join their parents in King's Lynn, where his father had a Chinese restaurant. It was a shock. Even today its population is almost entirely white. In the Seventies, the Yaus were the only Chinese family. At school and in the restaurant there was aggression. 'Settling in was hard. I hated the lifestyle,' he says. 'But we had no choice. As an immigrant, if you were Chinese you had to get into the restaurant business. And the Chinese are willing to make enormous sacrifices. Moving to small towns to avoid competition, long working hours for a low income, the racial abuse. The family paid a huge price.'

At 16, Yau was serving in the restaurant - though he never cooked. 'Special fried rice, chicken chow mein, sweet and sour ... To be honest, I really did not want to be involved in it. I really hated it.'

When the family took on a second restaurant in rural Lincolnshire, Yau moved out. He went to London and read politics and philosophy at City poly. A whole series of jobs followed - systems for an engineering company, an interior design business, until, inexorably, he found himself back where he started, behind the counter at a Chinese takeaway business, started in Peterborough with his father. It was 1986 and it wasn't where he wanted to go. 'But intuitively I felt I could not fail in the restaurant trade. And how else to build capital? I made back my investment in six months and I used the money to fund my research into fast-food.'

We walk around Tai Po's market, admiring the treasury of dried fish and shrimp, crucial for Cantonese stocks and stews. In one stall alone there are eight different grades and types of squid or octopus, and the same again of desiccated scallop. Yau looks as though he'd like to stuff a suitcase full - dried staples of this quality can't be had in Britain. We stop at the little temple, a dim, smoky haven. Yau is a Buddhist and later we make time to visit central Hong Kong's Man Mo temple so he can light an incense coil.

A few streets away from the market is the Tai Po McDonald's. Yau did time at this branch in 1990 after being offered one of the McDonald's franchises just opening up then in mainland China. He never considered it seriously though - his 12 weeks in a McTunic at the fryer and studying the managers' Black Book were really, he admits, industrial espionage. He had a Chinese fast-food idea. But the Tai Po experience put him off. 'We aborted the project - chiefly because of issues of de-skilling and portability.' As every Fast Food Nation reader knows, McDonald's and its like depend on a young, skill-free (and thus cheap) work force. 'But you can't take the skill out of wok cookery ...' A great fast-food idea remains a Yau obsession. There hasn't been anything new in the field since the birth of Pret A Manger in 1986, he points out - and he has a notion on the back burner. He won't tell me what it is. But, post-FFN , he promises that if it comes off he'll pay staff above the minimum wage.

It should be pointed out that Yau doesn't cook in his or his father's restaurants, or even at home. 'I think my attitude to cooking follows, a bit, what Bruce Lee said about martial arts - there's the spiritual and the physical side. But to attain ultimate enlightenment you have to do both. The physical side - it isn't so deep. But I can read and design a menu more easily than I can a balance sheet: I feel I've acquired the spiritual side and I can talk to a chef at every level. But I don't cook.'

He has a talent, though, for getting great people to cook for him, rather as he gets hot designers to design. The chef behind Hakkasan and that Michelin star is a Cantonese legend: Tong Chee Hwee, late of the Singapore Ritz-Carlton. The dim sum at Yauatcha are the work of another Singapore-Chinese master, Cheong Wah Soon. And Yau is demonstrably as much foodie as entrepreneur: enthusiastic, idea-driven, fascinated by the aesthetics of eating and the planning of the space in which it happens - 'the soft engineering' of the nosh-up experience. And, like any martial artist, he sought out the masters for his education.

His talk is peppered with ideas he's got from gilt-edged names: designer Philippe Starck, on the semantics of eating places and the creation of iconic brands (Starck was an early admirer of Wagamama. 'He told me: "You've created a phenomenon, a faith, a tribe who will follow you anywhere."'); the great interpreter of Thai traditional cookery David Thompson; architect John Pawson. Pawson worked with Yau on the Wagamama concept, its clear open spaces. Although minimalism is a style that Yau's restaurants have now rejected, he is still thinking hard in Pawson terms about the social dynamics of the space in which he puts people to eat.

Some critics, I point out, have complained bitterly about the Yauatcha space, his new dim sum house in Soho. It features a corridor too narrow for the waiters to pause in. At busy times, a 90-minute eating time is imposed: the social dynamic is a 'writhing, squirming pit of humanity crushed so close together they could probably identify each other's deodorant brands', wrote The Observer's Jay Rayner (who also said the food was 'marvellous').

'I don't like sedate,' grins Yau. 'The energy level is so high because of the spacing. It's not everyone's cup of tea ...' He speaks with the confidence of a man who knows that booking waits for Yauatcha (where you can drink 150 different types of tea) are two weeks long, and even longer at Hakkasan. His inspiration is clear - the next morning at an old-style tea house, we watch as the waitresses propel their dim sum trolleys along the aisles with the assured air you get when driving a battletank. 'I love this. It's so Hong Kong, the "get out of my way" style.'

We're now settled into a very under-engineered space, whose bare concrete walls and silver Lurex drapery is resonant of the low-budget rave club it once was. This is Yellow Door, a six-table hot ticket located in Hong Kong's wealthy central district. It's a 'private restaurant' - a name that dates from the days when licences were strictly controlled. Private restaurants are tiny, non-commercial places where chefs and customers collaborate in foodyism.

Yellow Door is owned and run by a well-known Hong Kong critic, Lau Kin Wai; the cuisine is 'nouveau Szechuanese'. 'Places like this are the first sign of Hong Kong moving on to a post-materialistic society,' says Yau. 'You need people to cook for the love of it: it's about working for passion not just profit.' We are four dishes down, on the second bottle of Merlot, and the table is dominated by a bowl piled high with different types of red chillis - plum, dried, bird's eye - and stalks of green peppercorns, garlic and mashed ginger. Somewhere inside there lurks morsels of pale chicken flesh. They seem to fizz and numb your tongue when you make contact with them. We're digging hard as Yau explains how elemental his soft engineering is.

'It's often about simple things, like lowering the table. That creates a different social order, less formal. There are ideal proportions for romance - the Venice Harry's Bar proportions - they're what I call the 38-68 rule. Height of seats between 34 and 38 cm, tables between 60 and 68 cm.' I am taking a saw to my dining table tomorrow.

It's now evening in Hong Kong. Europe has woken up and, as we eat, Yau has two mobile phones on the go. He's suddenly a little less the scruffy, passionate foodie and more the global restaurateur, the phone talk slipping seamlessly between his Cockney-tinged English and native Cantonese.

There are projects in Moscow and in Thailand to discuss. Back in London there are nearly 500 people - including Yau's Turkish wife of 11 years, Jale Eventok - working on the business. Bigger ideas are also fermenting: a Japanese successor to Wagamama (he was bought out of the business in 1997); taking Vietnamese cuisine - 'The next big thing from Asia' - and giving it a makeover; going into hotels, based on the Costes brothers' model, the Parisian cafe-owning limonadiers-turned-hoteliers (and lounge-music purveyors). 'It's a challenge. Not many food and beverage operations can migrate from one habitat to the other.'

Painfully early the following morning we are in the tiled halls of Ling Heung - Lotus Fragrance - dazed by the clatter of dim sum dishes from 100 or so closely packed breakfasters. This is the real thing. True dim sum - glutinous, stodgy, monochrome - arriving in baskets piled high in a trolley pushed by aproned ladies in a hurry.

From the har gau prawn dumplings to the cheung fun rolls and the chicken feet, it's all pallid whites and yellowish-browns - a long way from the exquisite confections of Yauatcha. Yau raves about the place, unchanged in a century. 'It's a ritual, a social gathering to pick up the gossip. The equivalent of going down the pub.' The 90 minutes you're allowed for dim sum at Yauatcha looks very generous - here we get ugly looks after 20.

We end the tour, bloated but very happy, with the best of Asian food: street snacks. We've tried the delicate little egg tarts from the shop in Lyndhurst Terrace beloved of Hong Kong's former governor, Chris Patten, whose fan letters are on the wall. We try the shrimp wan ton at Mak's Noodle Ltd. Mak Chi Ming, ninth-generation noodle soup purveyor, explains how you combine powdered dried flounder, dried shrimp roe and pork bones. It produces an exquisite, pinky gold consomme, which we drink like tea before chewing the fresh noodles.

'Incredible,' sighs Yau. 'The logic of it, the simplicity of the three components; the dumplings, the noodles, the stock. That's fast-food ... that's good.' There's a light in his eyes and I wonder if I'm watching the dawn of another bright idea.

· Busaba Eathai, 106 Wardour Street, London W1 (020 7255 8686); 22 Store Street, London WC1 (020 7299 7900). Hakkasan, 8 Hanway Place, London W1 (020 7927 7000. Yauatcha, 15 Broadwick Street, London W1 (020 7494 8888)