Is it a restaurant? Is it a club? Is it a kinked-up performance-art space? From where I'm sitting - a giant white bed in a huge white room, shared by 149 fellow diners/trippers/voyeurs - Amsterdam's Supperclub looks like a hallucinogenic mixture of all three.

We've just polished off a mignon de boeuf with spinach and shallot confit and French fries - our third course out of a promised five; Howie, the rambunctious American maitre d', is hoicking up his ra-ra skirt and sashaying across the floor to the lo-fi lounge emanating from the DJ booth, strewing handfuls of rose petals over passing punters as he goes; and here comes a dominatrix in a mesh body stocking and rubber apron, dragging an unprotesting 'victim' onto a chair, hog-tying him and shaving his head into a rather professional-looking Mohawk.

The level of attention you afford this spectacle - indeed, your general level of verticality - is contingent on the degree to which you've partaken of the stogie-sized spliffs being passed along the divan.

Pudding has now arrived; a raspberry creme brulee whose palate-cleansing effect seems enhanced by the fact that it's served in an ashtray. The woman next to me, who booked her place online three months ago from her native Australia, leans over from her semi-recumbent position, a beatific smile on her face. 'I've never been anywhere like this,' she announces, before being dragged off by the newly Mohawked man, now clad in a George Clinton-esque leather cape and codpiece, to get her bicep tattooed.

A lot of people have been expressing similar sentiments since Supperclub opened, five years ago. Any attempt to recount the experience soon descends into incoherence and is usually met with incomprehension; as with Vietnam vets and astronauts, only those who've been there can truly understand.

'It'll change your life,' gibber devotees on numerous restaurant-review websites. Many of them have made the pilgrimage from London, but soon they won't have to - if all goes to plan, the Supperclub will open in the capital next year. The site, an old church in Mayfair, has already been earmarked. 'London is so ready for a place like Supperclub,' says Douwe Werkman, a director of IQ Creative, Supperclub's parent company. 'We know that the British will be totally behind our concept.'

However, attempts to define that 'concept' by the masterminds behind Supperclub tend to suffer the same words-fail blight that afflicts their delirious punters. 'It's all about creative freedom in its many levels and manifestations,' is founder Bert van der Leden's attempt. 'Anything could happen here. It has that edge,' reckons Micky Hoogendijk, van der Leden's advisor and Supperclub's 'creative consultant'.

'What's it all about?' ponders Rob Wagemans of Concrete, the architects behind Supperclub's retro-futurist look. 'It's hard to get down on paper. We want to be market leader of all your senses, from the food you eat to the things you see to the music you hear. We had an old hippy sitting here one night who'd fried his brains on LSD, and he looked around and said, "In the Sixties, we thought the year 2000 would look like this".' Wagemans beams. 'To me, that was the ultimate compliment.'

In fact, Supperclub seems like a very Dutch compromise between hippy idealism and pragmatic commercialism. It was originally an anarcho-artists' collective with bug-eyed radicals squatting on mattresses plotting to overthrow multinationals.

The place was bankrupt when van der Leden, a former sailor, textile magnate and retailer, bought it in 1999. According to Hoogendijk, 'he had a vision for it. He wanted to keep the underground vibe, but also to create a beautiful space for a restaurant, make the whole thing theatrical.'

That sense of theatricality begins as you arrive; the club is situated in a dank alley that fittingly lies midway between the gentility of the Jordann and the sleaze of the red-light district. Its heavy steel door is unmarked, save for metal plaques bearing members' names (David Bowie is there, as, less predictably, is Michael J Fox). Inside, a right turn takes you downstairs to the toilets, marked 'heteros' and 'homos' (all-black, two-way mirrors giving uninterrupted views onto both sets of urinals), the members-only bar (all-red and densely curtained, very Twin Peaks), and the lounge (all-white with intimate leather banquettes).

A left turn takes you into the restaurant proper, with its two tiers of beds and open kitchen at the far end. 'It's a simple white box,' says Wagemans of the space, 'a blank canvas where people can do their own thing.' This licence extends from specially themed weeks dreamt up by creative director Bob Bruinsma (which have included the Supperclub Hospital, where leather-clad nurses placed bemused diners on gurneys and served them cocktails in specimen bottles, and Air Supperclub, where seats were arranged in aisles and meals placed on tray tables: 'I remember a bottle of wine fell to the floor at one point,' recalls Bruinsma, 'and Howie cried, "Ladies and gentlemen, we are experiencing some turbulence") to the preparation and presentation of the food itself. Supperclub has no menu; there's a 60 euro cover charge and, when you arrive at eight, you are simply asked if you eat meat or not before being served five courses at the whim of head chefs Joost de Bruijn and Michiel van der Eede.

'It's very liberating having no menu,' says van der Eede. 'It means that we can go for whatever's good at the market that day.'

With as many as 188 dishes to prepare simultaneously, the chefs work flat-out, particularly as they sometimes give their dishes a Supperclub tweak, adding a hypodermic syringe rather than a straw to a red-fruit milkshake. 'We served crucified guinea fowl once,' confides de Bruijn. 'We nailed its wings to a cross. But it didn't work. It wasn't the blasphemy, we just couldn't get all the birds to brown at the same time.'

If the food is a surprise (and generally much better than the gimmicks would lead you to expect), what's happening on the main floor can often create a frisson of unease; particularly if your waitress, having handed you a veal escalope, proceeds to lip-sync to Marilyn Manson while covering herself in raw liver and writhing around on the ground. There are limits to the loucheness, however. 'No sex,' says the tall, multi-pierced Patty, one of Supperclub's payroll performers (who also turns out to be the rubber-clad barber). 'This is a restaurant, after all. And if we tell you to sit down because the next course is coming, you have to do that or you don't get it.'

Supperclub's Rocky Horror playpen ambience has proved a major draw, with people basing their Amsterdam breaks around the likelihood of getting a booking (currently around three to four weeks ahead on weekends), and celebs clamouring to get a piece of the action (recent sightings have included Pink, Britney and bodyguards and the cast of Ocean's Twelve).

Its success has spawned a mini-empire, with van der Weden's parent company, IQ Creative, launching a Supperclub cruise (a three-deck boat plying the waterways around the city), and opening a second Supperclub in Rome a year ago, which has become the Italian capital's hottest spot for see-and-be-seen types. A third Supperclub is due to open in San Francisco's SoMa district before the end of the year, and the London site will be the fourth. But will its ubiquity work against a set-up that prides itself on its underground credentials? Is Supperclub becoming Starbucks?

'That won't happen,' says Hoogendijk emphatically. 'Supperclub has grown organically, and each one we open will be subtly different because of the local sensibilities. For example, there are nuns living above the Rome Supperclub. It's a lot more conservative than Amsterdam - the Italians refuse to take their Prada shoes off when they lie on the beds. I think the one in San Francisco will be just wild.' And London? 'Oh my God, I can't imagine what London will be like,' she says. 'We might have to employ security or something there. You guys are so strait-laced, but you go crazy when you're let off your leashes.'

'Everyone wants to open a Supperclub,' says Douwe Werkman, a director of IQ Creative. 'But first we scout out the city to make sure it has the right vibe. There has to be a thriving alternative art and music scene. We'd like to open one on every continent, but it's really important that it is unpredictable, that it doesn't become a souvenir T-shirt thing.' To that end, Supperclub doesn't accept stag or hen party bookings. If 'special' means singular, the night I attend is more than fulfilling the Supperclub brief. The Australian woman has returned with her tattoo, a bunch of swirly blobs, which she's pretty sure isn't indelible, but hey, you know, whatever. We recline and watch the Mohawk-and-codpiece guy, whose name is Sanjay, clamber onto the bar to bump and grind as Frankie's Relax throbs from the PA.

At some point the main space morphs into a dancefloor and I'm led off for a Thai-style massage; then everything goes a little woozy. The next day, when trying to piece these events together, I realise why any attempt to recount the essence of the Supperclub 'happening' is doomed to failure. As Douwe Werkman says: 'The best nights in Supperclub unfold like a kind of dream. You look back and think, "did that really happen?" He smiles. 'I don't think too many restaurants give you that kind of experience.'

· Supperclub, Jonge Roelensteeg 21, Amsterdam. (0031 20 344 64 00; www.supperclub.nl)