It is while we are being served the fifth course out of 16 - a vibrant green lettuce soup, spooned over a sweet-onion custard - that our French waiter apologises for the quality of his English. We tell him not to worry. After all, we are in the flagship restaurant of French super-chef Jo'l Robuchon, and in a place like this you want the front-of-house staff to have an accent you could cut with a knife. Plus the dish he is describing is divine, as indeed is the entire restaurant. The dining room is dressed in regal shades of purple, with a flowing, intricate motif that repeats from curtain to carpet to knife handle. There is a chandelier by Swarovski, a trolley with 12 different types of bread and another with 25 different types of petits fours, plus a wine list as thick as a paperback book. In short, it is everything you would hope a Parisian temple to high gastronomy might be.

Except we are not in Paris. We are not in France or even in Europe, as a quick peek out of the huge front doors would quickly tell you. Because there, just 12 paces away across the swirling carpet, is the first of many thousands of slot machines. We are instead at the MGM Grand Hotel in Las Vegas and we are enjoying a $350-a-head tasting menu - before taxes, wine and service - possibly the most expensive single dining experience available in the US today.

A few years ago, the notion of such a thing in Las Vegas would have been unthinkable. Back then eateries, like the hotel rooms, were treated by the casino owners as an amenity; something gamblers needed to be given cheap while they spent their serious money at the blackjack tables. Vegas was the city of the all-you-can-eat $6.99 buffet. Over the past decade, however, a revolution has swept through the world of high-end dining which has changed all that. Gone are the days when top chefs laboured for the first 10 years of their careers to gain their three Michelin stars, and then spent the rest of their days burnishing them. Now, any big-name chef worth their (Oshima Island Blue Label) salt has to have not a single restaurant but an empire. And a big one at that. Finally, haute cuisine has gone global. And Las Vegas, forever in search of new sources of revenue, has become ground zero for the phenomenon.

A short cab ride away from the MGM Grand, where Robuchon has not one but two restaurants, is the Mandalay Bay hotel. On the 64th floor is Mix, the $22 million restaurant of French chef Alain Ducasse, where you can eat versions of the dishes he serves at his three-star restaurants in Paris and Monaco. Down the other end of the Strip, at the Hard Rock hotel, is Nobu Las Vegas. In between, at Caesar's Palace, they are putting the finishing touches to the first restaurant outside France from French three-star chef, Guy Savoy. 'There's now a group of people who go from city to city eating in these restaurants,' Jo'l Robuchon told me in London, a few weeks before my trip to Vegas. 'It's reassuring for the international traveller to know they can go from one of my restaurants to the other because they can order the same food. '

The global picture bears this out. As well as his two restaurants in Vegas, Robuchon has branches of his L'Atelier format - a more casual eatery venture compared to his lead restaurant at the MGM Grand - in Paris, Macau and Tokyo, with others planned in New York, Hong Kong and, later this year, London. Nobu Matsuhisa opened his first Nobu in New York in 1994. Today he is in Milan and Tokyo, Mykonos and St Moritz, Miami, Aspen and London (times three). As well as Paris, Monaco, New York and Las Vegas, Alain Ducasse has restaurants in - among other places - London, Beirut, Hong Kong, Spain, Switzerland and Tokyo. Pierre Gagnaire is in Paris, London and, soon, Tokyo (everyone is in Tokyo).

Britain's chefs are getting in on the act, too. As well as his two restaurants in London - Hakkasan and Yauatcha - Alan Yau has projects underway in Moscow, New York and Hong Kong. But the real trailblazer is, of course, Gordon Ramsay. He has had a restaurant in Dubai since 2001 and another in Tokyo since last year. This year he opens his first in New York, with new ventures to follow in Miami and Los Angeles. 'We're closing Royal Hospital Road during the summer and installing an £80,000 webcam system in the kitchen,' Ramsay tells me, proudly. 'That way I'll be able to see what's going on in all my restaurants around the world. We'll have clocks up for the different time zones, too. It will look like a f*****g investment bank in there.'

How did this happen? How did top-end restaurants - which were meant to offer a bespoke experience, in which the hand of the chef whose name was above the door was assumed to have touched the food you ate - turn into international brands more akin to Gucci, Chanel or Armani? David Nicholls, executive chef at the Mandarin Oriental Hyde Park Hotel, and a highly respected veteran of the catering scene, puts it down to a seismic shift in hotel dining. 'Up until two decades ago it was very fashionable to eat in hotel restaurants,' he says. 'In London people went to the Connaught or the Savoy, for example.' But then a new breed of chef emerged who wanted to set up independent restaurants. In London there was Marco Pierre White and Nico Ladenis and Pierre Koffman. 'They started to dominate the workforce and the young talent wanted to go with these independents.' As a result the hotel-dining experience fossilised. 'Restaurants had been a cash cow to the hotels. Now they were losing money and they weren't able to refurbish rooms.'

The solution was to bring in star names to run those hotel dining rooms, a notion which coincided with a boom in media interest in food and cooking. Still, there was resistance in the chef world to the notion that a top name could be in two places at once. It took Alain Ducasse to prove it was possible to run more than one top-class restaurant when, in 1996, he took over a hotel dining room in Paris to go alongside the three-star operation he already had in Monaco. Within eight months Michelin awarded him his second set of three stars. (Last year he became the only chef in the world to have three sets of three stars, when Alain Ducasse at the Essex House in New York was awarded the accolade by the newly arrived Michelin Guide.)

A starting gun had been fired. Nobu opened in London at the Metropolitan Hotel near Hyde Park Corner in February 1997. Since then the restaurant's British-born head chef, Mark Edwards, has become executive chef for the whole group, overseeing openings across the globe. 'I've opened the last 10 Nobus,' he says, 'And it becomes easier every time. It's easier to source the product, for one thing.' One of the first things they do when sizing up a new location is check out the fish markets. 'Today there are lots of things we can fly in. We can bring in soy sauce and various other Japanese ingredients. But we also need to be able to get as much fresh produce on site as we can.'

So what defines the kind of location where a Nobu can work? 'It needs to be fairly cosmopolitan,' he says. 'We need a city really. There has to be a restaurant base - an interest in food - a little bit of money and of course access to the ingredients.' Meanwhile, from their side, they have to be able to supply talent. 'We are constantly encouraging our chefs here because they are often the ones who will go out and open each new Nobu for us.' They are currently working on new openings in Melbourne and Moscow. The latter will be the largest Nobu in the world, capable of seating 300 people at any one time. I ask him if he thinks there are any downsides to the spread of restaurant brands like this. Edwards shrugs. 'I suppose eventually it could be a bit like the big supermarkets putting the corner shops out of business. Small local restaurants might suffer.' For now, though, nobody is complaining. Nobu currently has a worldwide turnover of £120 million.

In the autumn of 2001, shortly after Nobu had opened its 12th branch, Gordon Ramsay got in on the act when he took over the catering operation at the Dubai Hilton. A couple of months later, and closer to home, he opened Gordon Ramsay at Claridge's. A year after that he brought Angela Hartnett back from Dubai and installed her at the Connaught. That was followed by a series of ventures at other hotels across the capital. 'There are two ways of doing these things,' says Christopher Hutcheson, Ramsay's father-in-law, who runs Gordon Ramsay Holdings, a business with a £30 million-a-year-plus turnover. 'Either you can do a consultancy, where you get paid for your services but don't actually own the restaurant, which is what we do in Dubai and Tokyo. There we supply the 10 most important members of staff and they do the rest. The other model is to actually take it over.' In other words they rent the space, deal with the costs and take home all the revenues. 'For us we think that's the better model. We just have to find the right partner.'

Hutcheson admits it's a challenge. 'When you're looking at opening a restaurant in a different city you have to ask exactly what is it people want? Can we supply it and how do we have to change what we do to fit that?' The real challenge, he says, is the shortage of Gordon Ramsay's time.

Hence Ramsay's new webcam system, which the chef is clearly very excited about. 'I wouldn't open all these restaurants unless I knew the dishes would be spot on,' Ramsay tells me. 'But it's definitely do-able. Look at Ducasse. He delivers three stars in New York, Paris and Monaco.' But can Ramsay really provide exactly the same experience across the globe in London, New York, Tokyo, Los Angeles and Miami? 'The type of ingredients we use may be different. It may be line-caught sea bass here and striped bass there but the integrity of the dish will be the same.' And what about the criticism that, if Ramsay's name is on the menu, he should be the one at the stove? 'People ask me who does the cooking when I'm not there and I tell them it's the same people who do the cooking when I am there. I remember being asked that question by a journalist in a very expensive Armani suit. I asked her whether she thought Giorgio had stitched every single seam on her suit. Obviously not.'

Still, Ramsay admits he's 'shitting himself' about the forthcoming launch in New York, which will be in the Rihga Royal Hotel on West 54th Street. Nevertheless Ramsay's convinced he's installing the right man as chef. 'Neil Ferguson was with me at Aubergine. He was Angela's head chef at the Connaught. We've sent him to eat in 162 restaurants worldwide. We have that level of trust.'

For his part, Jo'l Robuchon admits he, too, could never have built his global empire were it not for the people around him. When he retired from his Paris restaurant in 1996, having been declared chef of the century, he said he had laboured long enough. Then suddenly, in 2003, he was back. 'Trusted colleagues of mine wanted to open a restaurant but they couldn't get money from the bank so they asked me to lend my name to it,' he says. 'Right away I said I wanted to do something simple, not three-star.' The L'Atelier brand is certainly that. Decked out in black and red, with huge, backlit jars of preserved fruit and vegetables as ornaments, the original branch on rue Montalembert in Paris looks like the set for an 80s Athena poster. Diners sit at a bar around an open kitchen and cooks hand dishes out as and when they are ready. Some are as simple as a plate of perfectly cut Spanish ham. Others, like a chestnut soup with crisp bacon are a little more complex. But none of them is exactly intricate. 'L'Atelier is about simplicity,' Robuchon says.

And exportability. Because he has so many experienced people working with him Robuchon believes he can maintain standards all over the world. For example, the branch of L'Atelier at the MGM Grand in Las Vegas looks exactly the same as that in Paris and serves an almost identical menu despite the fact that they are nearly 6,000 miles apart. Given this interest in simplicity, I wonder why Robuchon also set up the high-end gastronomic restaurant next door to L'Atelier with the $350 tasting menu that I enjoyed. 'I was approached by the president of the MGM Grand, Gamal Aziz,' Robuchon says. 'And I said no. The problem is he's very charming. He was just too persuasive. Plus he said I could have anything I wanted. He never talked about profitability. He just wanted the best.'

For the international chefs now crowding into Vegas - and the many other cities around the world like Moscow, Dubai and Tokyo - this is the appeal. The hotels are offering irresistible deals. Usually there will be a consultancy fee, plus a promise of five per cent of the turnover. As a result the chef will make money whether the restaurant goes into profit or not. Though if it does they get 10 per cent of that too.

At Caesar's Palace I am given a tour of the building site which will be the new branch of Guy Savoy, by his son Franck who, at 26, will be managing the venture. He leads me through private dining rooms with glass walls two inches thick, past monumental screens in dark hardwood, to what he says will be the location of the best table in the whole restaurant. Across the road from Caesar's Palace is the Paris Las Vegas hotel complete with a quarter-size version of the Eiffel Tower. From Guy Savoy in Paris you cannot see the Eiffel Tower even though it is less than two miles away. 'But from this table at Guy Savoy you can,' Franck says with a grin.

I ask him if he and his father had any doubts about this project. 'The French press said you don't know what you're doing; the Americans don't know how to eat; there is no produce. But I ask, "Do you know Las Vegas?" and they say, "No".' And then he says, 'I'm not wasting my time here. It's a big project. Caesar's Palace has given me everything I need to do the job.' As to getting the produce, that is no longer a problem. The city's airport is only a 10-minute drive away and every day planes, bearing tonnes of the very best ingredients available in America, pull up to the side of the airfield where they are unloaded into cold rooms and from there straight into refrigerated vans.

It supports an extraordinary restaurant scene. I visit Bouchon at the Venetian hotel, an exact replica of a French bistro, down to the tiled floor and engraved mirrors. It is owned by Thomas Keller, chef at the French Laundry in California and Per Se in New York. He is generally regarded as the best chef in America; certainly his cooking is touched with genius. We are in the middle of the Nevada desert but the terrific food - fruits de mer for $98.50, steak frites for $34.50, a croque madame for $17.95 - is pure Paris. Later, I have drinks at Aureole at Mandalay Bay, owned by American celebrity chef Charlie Palmer, where the main draw is a 42-foot wine 'tower', containing over 10,000 bottles. When customers place an order for wine, via a wireless tablet PC brought to their table, the bottles are fetched by 'wine angels', tiny women in black catsuits who fly up on ultra-thin cables as if they are in Mission Impossible.

At Nobu Las Vegas I eat the same dishes as I tried in London - black cod with miso, yellowtail with jalape-o and coriander - and though the presentation is a little different they taste exactly the same. At Ducasse's Mix, where they had to fly the stove in on a helicopter, I gawp at the prices - $30 a starter, $50 a main course and up - and at the glittering view of the Las Vegas strip below us. In 2004, non-gaming revenues - money made from high-end hotels, restaurants and shops - overtook gaming revenues in the city for the first time. People now come to Vegas not to visit the casinos but to eat. They come to spend $75 on tournedos Rossini at Mix.

There are those, however, who warn that there can be drawbacks to a restaurant boom like this. 'I don't want to speak down to Alain Ducasse,' says Greg Waldron, Vice President of Food and Beverage at Caesar's Palace and the man who brought Guy Savoy to the hotel. 'But he's everywhere. What he's doing at Mix isn't the real Ducasse.' The other charge - which applies to branded restaurants all over the world, is that of absenteeism. 'There are chefs in this city with their names above the door who haven't seen their kitchen in a year,' says Gamal Aziz, the man responsible for bringing Robuchon to the MGM Grand. 'The chefs I hire see the business the way I do. Joel Robuchon has been here once a month for a week each time since we opened back in September.'

He is in town the night I go to eat at his restaurant and, for a while, he sits at my table watching me eat his food. He points to a black-and-white photograph on a shelf next to me: the picture is of Robuchon standing next to Celine Dion. He pats the table. 'This is where Celine sits when she comes,' he says, proudly. A little later the sommelier asks Robuchon if he will sign the label of a bottle of wine that a table of Japanese diners has just finished, and which has been taken off and put into a presentation card. It is for a Chper thousandteau Latour 1959, yours for around $5,000. When we met in London a few weeks before I asked him what he thought of Las Vegas as a place. 'I always have fun in Vegas,' he said. 'I love the city.' It's really not that hard to see why.

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