Shopping for his precious spices is something Vongerichten clearly enjoys when visiting the UK, relishing the fact that the spices are imported directly from south-east Asia. "Lemon grass and ginger are grown in the USA and so you're not allowed to import them, but here you get the best spices possible, straight from Malaysia or China."
Eating out is important for Vongerichten, too, and he believes London is the most exciting city for food in Europe at the moment. He does not gravitate automatically to his own type of food, either. The River Café [Ruth Rogers and Rose Gray's modern Italian restaurant in Hammersmith] was "fabulous", he says.
"They gave us bruschetta with sautéd porcini, just two ingredients - parsley and porcini - on a piece of bread. That's what food is all about, confidence in the ingredients and letting people recognise the food they're eating.
"If we offer lobster with Thai herbs or foie gras with ginger and mango, people know what they're eating; if it takes three lines to describe, then people are confused."
After his book-launch party at Vong in the Berkeley hotel, Vongerichten was due to sample Vineet Bhatia's modern Indian food at Zaika.
Eating at Marco Pierre White's Oak Room restaurant at Le Méridien hotel, Piccadilly, was a highlight of a previous visit to London: "It was classic, with some touches - he did a wonderful turbot roasted on the bone with a little curry."
A conversation with Jean-Georges Vongerichten leaves an apparently contradictory impression. He comes across as complex: a chef whose food, particularly that served in his Vong restaurants, is a controversial marriage between a classical French background and a passion for the spices of south-east Asia. He is the chef who dares to put capers and raisins together, creating a culinary sensation that has since been picked up by other top chefs, and the chef whose influence spans three continents with no sign of fading.
But it is simplicity that Vongerichten appears to value most. "One of our dishes at Vong is seared foie gras served with mango and ginger sauce. That's three ingredients on one plate. It's so simple. For me that is what food is all about."
Vongerichten's latest book, Simple Good Food (published this month by Kyle Cathie, £19.99), expands on this philosophy. "There is an assumption that cooking with spices is difficult. It's not - but you have to find the right spices and know what to do with them. Some people just mix and mix without extracting the right flavour. With lemon grass, for example, it's not just a case of chopping it up and throwing it in - you have to bruise it first."
Refreshingly, Vongerichten is not precious about suggesting using a prepared curry powder, particularly, he says, given the good quality available in the UK. "A home-made curry powder needs 13 ingredients, but the recipe for curried mussels is just mussels, shallots, sweet wine, creme fraiche and curry, so if you buy a good powder you don't have to worry about 13 of the ingredients. That makes it simple."
Despite Vongerichten's insistence on simple ingredients and techniques, all the recipes for dishes served at Vong restaurants are stored in a computer program that chefs are expected to follow to ensure consistency throughout the Vong empire. "Using spices is like being an alchemist. If you put too much cardamom, cinnamon or star anise in a mix it will change the whole thing. It's important to be accurate," says Vongerichten.
As a result, lobster with Thai herbs ordered in Hong Kong's Vong will taste the same as lobster with Thai herbs ordered in Chicago. Consistency also means it is easy to clone the Vong concept, and Vongerichten admits that a few more could be opened around the world to add to the existing four without requiring him to be involved on a daily basis.
He wouldn't dream of cloning his other restaurants, however, particularly the ultra-chic Jean-Georges flagship restaurant in Manhattan, where he spends most of his time, or even the ultra-trendy Mercer Kitchen that opened in summer 1998 to rave reviews. These are the very personal restaurants, the ones in which he wants to preserve his identity rather than cook to a formula in the way of Vong.
All his restaurants, however, demonstrate an equal obsession with flavour. "There's no way back to bland, flat food or to the food we were eating in the 1970s or 1980s. Now people are eating out seven times a week - they're at Nobu for lunch, here for dinner, at Marco Pierre White the next day - and the more people go out to eat, the more they want an exciting experience and new sensations."
There's a health issue, too. If people eat out so much, Vongerichten argues, they want lighter, more digestible food; cooking based on herb-infused oils, emulsions and vegetable essences, rather than cream, butter and heavily reduced stocks.
And while Vongerichten recognises the French influence on his food - he is from Alsace and trained with the likes of Louis Outhier and Paul Bocuse - he makes a crucial distinction. "French food has the reputation for being heavy, but that's Escoffier food, which is not real French food. Real French food is from Alsace or Burgundy. There's no cream in dishes such as cassoulet or sauerkraut, and I never saw my mother doing a hollandaise or beurre blanc."
It was a stint at Outhier's restaurant L'Oasis, near Cannes, in 1976 that opened Vongerichten's eyes to more-refined cooking. "That was the first time I used basil and thyme. The only herb we had in Alsace was parsley, and I'd never tasted olive oil."
Outhier encouraged his protégé to spend time in Thailand and in 1980 his love affair with spices began. "I got off the plane and the smell in the air was different. I soon came across the classic Thai soup - tom yam - and asked ‘how do you do this?'. A pot of water, lemon grass, mushroom, cream and fish sauce, they replied. You end up with the best soup in the world. It was so different from what I'd been learning. This food is quick, light, and you're not eating it for the next two days."
Vongerichten spent four years in south-east Asia with stints in Bangkok, Hong Kong and Singapore, and the result is the French-Thai fusion of Vong. Rabbit is slow-cooked in the traditional way of a French stew, but it's a curry, finished with a little coconut milk; foie gras is served with mango and ginger.
The twist on roast chicken (served with lemon grass and sweet rice in a banana leaf) has been on the Vong menu since day one, and the sea scallops with the famous caper raisin emulsion has become a signature dish. "I found it by tasting capers and raisins one after the other and it was like mustard in my mouth. We combine one-part dry raisins, one-part capers and one- part water, blend it with some vinegar and nutmeg and serve it with caramelised cauliflower with the scallops."
His pet hates include what Vongerichten calls "zoo food" such as kangaroo or ostrich meat. He prefers to take a basic meat - for him there are no new food groups, just new ways of presenting existing ingredients - and make it taste different.
"We buy the best scallops or the best foie gras, chicken or beef and add spices to give a new dimension. Seventy per cent of good cooking is down to good product, understanding it and adding a touch to make it different. I want people to taste my food and say, ‘Wow'."