Sketch, London

The Michelin-starred chef Pierre Gagnaire has brought his culinary tricks to London - and the result is wildly extravagant in all senses, says Tracey MacLeod

Sketch is the most exciting, absurd and expensive restaurant in Britain. A pleasure palace dreamed up by Mourad Mazouz, of Momo fame, and Pierre Gagnaire, one of France's most revered chefs, it is fantastic in every sense of the word, a shrine both to modern design and to gastronomy.

The Millennium Dome should have hired Mazouz as project co-ordinator. Had the Dome contained anything as astonishing as Sketch's ostrich-egg toilet-pods, as exquisite as the cakes displayed in the tearoom, as opulent as the crystal-studded powder rooms, visitors would still be queuing outside. (Mind you, it probably still wouldn't have opened, judging by the ruinous over-run of Sketch's rumoured £11m building programme.)

It would be easy to spend One Amazing Day in Sketch. Within its enormous Mayfair premises are two bars, one of which serves lunch, a tea-room offering all-day snacks, a video-art gallery that changes into a dining room at night, and a fine-dining restaurant, the Lecture Room. I'd originally planned to review the latter, until I was made aware of the prices – starters cost £30 to £48, and main courses £40 to £75, meaning the bill can easily reach £250 a head. Figuring that The Independent's budget could be more usefully deployed, I changed my dinner reservation to Gallery: cheaper, at around £50 a head, and a lot funkier than the ultra-formal Lecture Room.

Walking into the enormous, high-ceilinged Gallery is like stumbling across some missing set from Terry Gilliam's Brazil. It's a mad fusion of an all-white art gallery with the Reading Room at the British Museum. Video art is projected onto the walls to form a spooky rotating frieze, there are occasional gusts of incense, and a soundtrack of bleepy music completes the sensory disorientation.

And then there's the food. Gallery's head chef worked under Gagnaire in Paris and his menu serves as an entry-level introduction to his boss's experiments with temperature and texture. In other words, if you like lots of small dishes of tepid and unidentifiable ingredients, you're laughing. Starters are served from designer dim-sum trolleys, and are meant to be shared. We took all six between the three of us (for £22), which sounds greedy, but each little dish afforded us about two mouthfuls each.

As for what they contained, well, we were flying without radar. Ingredients had been diced and mushed, and dishes bore little relation to their menu description. A layer of caviar suspended in tea-flavoured jelly yielded to reveal smooth, creamed potato. Beef tartare was spiked with sea bream, herring and smoked cheese. Cubes of gelatinous mi-cuit salmon were partnered with dates coated in almond powder. If the design recalls Terry Gilliam, the food is definitely Peter Greenaway.

Main courses also come in portions that might politely be termed "dainty". Seared foie gras, served very hot, but so lightly cooked it was almost liquid, came with shredded magret of duck, and a fudgey jam of figs and walnuts. Fricassee of Dover sole was another serious and well-constructed dish, built on a delectable vanilla-scented vegetable nage. The joker in the pack was a strange-tasting monkfish tempura in a Guinness and apricot reduction, which reminded its recipient of Toilet Duck.

Like the starters, desserts are served from trolleys – a nice idea, which means that you can see the food before ordering it. Palm-fruit tapioca came with a crunchy topping of pistachio and praline, while citrus Madeira cake was a pineapple upside-down cake with a good stylist.

Some of the dishes were spectacular, but we were left oddly dissatisfied, as though we'd dined on a banquet of starters. Perhaps it was the all-white environment, but it almost felt as if Sketch was some kind of elaborate experiment, and we were the lab rats. They've even pushed the envelope with the envelope that contains the bill – it's made out of sandpaper.

But there's one piece of design that sticks in the mind – and, if you're not careful, could impale itself on your tongue. It's the hybrid spoon/fork you're supposed to eat your dessert with. It doesn't really work – you can't reach the edges of the bowl with it – and in yoking together two things that work perfectly well without each other, it symbolises Sketch's eccentric synthesis of food and fashion.

A few days after my visit, I retained a clear memory of the design (not to mention the chilling moment of realisation that the only person in the place older than me was Nicky Haslam), but the details of the food had evaporated. Just like one of those modern musicals where you come out humming the scenery. But what scenery! You really have to go, as no one in their right mind ever said about the Millennium Dome.

Sketch, 9 Conduit Street, London W1 (0870 7774488)