Hibiscus, Mayfair

London Restaurant Festival, which concludes on Monday, has been like Christmas to the food-obsessed among us. In only its second year, the LRF has grown from a week-long affair in 2009 to a full-on fortnight in 2010, with hundreds of restaurants offering special menus, American Express sponsorship and a packed programme of high-profile gala events. Of these, the most filling was the insanely abundant launch breakfast at Roast - I really did expect John Cleese to emerge and offer "just weurn waffer theen meent" - and the most fun was the Big Quiz, held over the course of a delicious three-course feast at Le Cafe Anglais and hosted by none other than Anne Robinson - as you can see, we bonded over our shared hair colour.

The most cerebral however was the Big Debate. Held at King's Place and chaired by the debonair human rights lawyer Jason McCue, it pitched Rosie Boycott and Janet Street-Porter against Jonathan Meades and A.A. Gill to debate the motion 'This house believes that French cuisine is a spent force'. So, nothing controversial there then. Warned by McCue not to be lured down the lazy path of Francophobia, the ladies' team, speaking for the motion, bemoaned the demise of French agriculture and the increasing prevalence of the motorway service station, while also praising the ever-improving quality of food and cooking in Britain (a moment of comedy came when JSP, giving a roll call of British chefs, invoked the name of Richard Corrigan only for the man himself to precise from the audience "I'm Irish!")

The gentlemen meanwhile spoke glowingly of the innumerable fine restaurants, shops and manufacturers throughout l'Hexagone (Meades) and of the Proustian memorability of the first taste of a real French croissant, butter and confiture (Gill, whose participation in a debate about a spent force struck me as ironic). Points were awarded or deducted by questioners from the audience as well as McCue and the motion was eventually defeated, albeit by only the narrowest of margins.

Anyone who believes that French cuisine - cuisine in its literal sense of cooking - really is a spent force can not have had the lunch that I had at Hibiscus last Sunday. Chef-patron Claude Bosi's two Michelin-starred restaurant on Maddox Street is renowned as being one of the country's, not just the capital's best so you would expect the experience to be pretty stellar, but add to this the fact that Bosi's co-chef for the day  - under the LRF's American Express-backed 10-10-10 initiative - was none other than Alain Roux, he of the three-star Waterside Inn in Bray, and you can begin to imagine just how spectacular the meal was.

We  - being myself, Alyn and our gorgeous NBFF Chloe - began with an amuse bouche of Hibiscus soda topped with black pepper-infused citrus foam, which was lively, bracing and tart, perfect for prepping our taste-buds for the seven courses to follow (although the Pol Roger we were sipping at this point was also doing a pretty good job.)

First we enjoyed Roux's terrine of pressed foie gras and supreme of guinea fowl with truffle and young red chard leaves. This was flawlessly executed, the dense supreme in the middle of the velvety terrine creating a beautiful complementary texture, although the most exciting part of the dish was the teeny tiny pickled mushrooms - I'm afraid I've no idea what variety - which dotted the plate. Next up was pan-fried lobster medallion - the claw also making a welcome appearance - with white port sauce and ginger-flavoured vegetable julienne. This was how I like my men to be, simple, elegant and rich, and there's nothing that's not improved by a bit of ginger, as Anne Robinson might say.

Claude Bosi took over for the next two courses and this was reflected in the solidly British ingredients, cooked to classically French techniques. First was roast hand-dived scallops [sic - each portion was a singular, though huge, scallop], pork pie sauce, pink grapefruit and wood sorrel. Each scallop was crusted with a mix of herbs and apple, which brought depth to the otherwise light dish. The pork pie sauce - which really did taste like that most perfect of snacks and which I would dearly like a large bottle of to splash over everything - was a witty addition, although we all agreed that the pink grapefruit, served as a teaspoonful of thick syrup, was just too sharp and overwhelmed the sweetness of the plump scallop.

The next, nominally main, course however was just about perfect; Shropshire mallard, a nice nod to Hibiscus's original Ludlow location, poached in grape juice and served with sweet potato and saffron. In my enthusiastic amateur's opinion, this was about as good as food gets: the tenderest meat, well-judged accompaniments (the sauce included a handful of lovely poached grapes; the potatoes were whipped into a smooth, saffron-scented purée), elegantly plated and served in just the right quantities. Then followed a pre-dessert - what used to be known as a 'palate cleanser' - of apple salad, sweet celeriac and chestnut cream, which tasted rather like stewed apple baby food, or Colman's apple sauce, but looked pretty and straddled the savoury/sweet axis most efficiently.

Each chef had created a dessert, one the epitome of traditional French cuisine  -Alain Roux's textbook pistachio crème brulée - the other boldly contemporary, being Claude Bosi's cep tart with macadamia nut ice cream. Yes, cep as in mushrooms; Bosi had conceived a tart of very sweet short crust pastry with a sweetened, but unmistakeably, earthily savoury filling, the ice cream adding salt and smoke. When I told smarty-pants James Ramsden this the next day he looked at me as a resigned parent would at their idiot child and said "It's called umami dear" - but I'm sure you all knew that anyway. As a table we unanimously loved the crème brulée but couldn't reach a consensus on the tart; I for one thought it was fantastic, as were the hand-made chocolates which accompanied the delicious, tar-thick rocket fuel coffee.

I've focused firmly on the food thus far - and to be fair, how could I not - but other brilliant bits deserve a mention. Right at the start, even before the gorgeous baked in-house sourdough bread and unsalted French butter were brought to the table, we'd been treated to a basket of Bosi's signature piping-hot goujères - addictive Parmesan and Cheddar-cheese filled puffs resembling incredibly posh dough balls. The wines chosen for us to accompany the menu were exceptional: a crisp, light, treacle-yellow 2002 Ribolla, Gravner from Italy; a big, complex, more-fruit-than-Carmen-Miranda's-hat Vinsobres Cote de Rhone Villages, and with our brace of desserts an unusual Ice Cider from Quebec, a North American version of cider brandy but with a deeper sweetness and extraordinary length.

Service was absolutely impeccable; the wines were presented to us by easily the most enthusiastic and engaging sommelier I'd ever encountered, and our food brought and introduced by an equally committed and lovely (not to mention preposterously handsome) waiter who expertly tempered respect for formality with judicious humour and panache. My particular favourite touch - whether practised or not I couldn't tell but I loved it anyway - was both the waiter's and sommelier's habit of making suggestions rhetorically; "Shall I arrange a drop more of that for you?" in response to an empty glass, or "Would you be feeling ready for your desserts now?" which have the effect of making one feel terribly clever for simply saying "Yes". It's a highly enjoyable form of cosseting which I could get dangerously used to.

Alas I'm unable to tell you what this three hour Bacchanal cost, not because it was free as I know some readers might be thinking from all the references to American Express (from whom I have not received so much as an additional membership reward point) but because it was extremely kindly and generously paid for by our lady host and it would have been rude to ask. What I can tell you, as a guide, is that three courses a la carte at Hibiscus is usually £75, with offers at lunchtime and a tasting menu at £80 for six courses. This makes it rather more affordable than the Waterside Inn, whose prices left me breathless when I researched them.

Hyperbole is an occupational hazard in food writing - I remember how I used to flinch when, in every one of her mercifully now discontinued reviews, one free-sheet critic would refer to her having been 'in raptures' at one dish or another - so it's with careful aforethought and the space of a week's reflection that I can say that this was one of the best meals I have ever had. Hibiscus shows that French cuisine is no more a spent force than the vibrant, vital culinary scene which London Restaurant Festival champions and which right now is one of the most, perhaps the most, exciting in the world. And that's not open to debate.

Hibiscus, 29 Maddox Street, London W1S 2PA Tel: 020 7629 2999 http://www.hibiscusrestaurant.co.uk