Chiltern Firehouse, restaurant review: The menu here is a tempting tour d'horizon of current food obsessions

Call the emergency services! I'm stuck in a fallen tree, pinioned by its branches, while a frantic rescue operation is being mounted. The scenesters around us are coolly looking on as wine glasses topple and waiters scurry to release me. Where's a fireman when you need one?

Not round here, not these days. The old fire station which houses London's hottest new restaurant was decommissioned in 2005, and the extravagant Gothic building expensively renovated as a designer hotel. The garage, once home to the fire engines, now revs with the self-congratulatory hum of a fashionable crowd, who have scored a table despite a bookings policy apparently borrowed from the North Korean tourist board.

Once you're in, though, the staff practically hose you down with hospitality. The ratio of front-of-house personnel to customers approaches 1:1. When a waiter accidentally nudges over the magnolia tree, it's purely a problem of over-crowding – the room is generously spaced, but packed with waiting staff.

To find such a crucible of foaming fabulousness in the backwaters of Marylebone is surreal. Chiltern Street is the high street time forgot. It's where you might come in search of an oboe reed, or a pair of outsized shoes (there's an inexplicable cluster of shops for the unconventionally shaped here). But this slice of A-list action, the UK debut of New York hotelier André Balazs, blasts the area straight into the near-future, bypassing most of the past 70 years.

There's a NYC vibe to the place, with its sharply-costumed greeters and throngs of beautiful rich people (no place here for the unconventionally shaped). The dining room, too, doesn't look like anywhere else in town. They've kept the huge firehouse doors, giving an almost rustic feel, while cleverly-placed mirrors create the illusion of infinite space. And there's a theatrically open kitchen, in which the full spectrum of cheffly beards are on display. Chief among them is executive chef Nuno Mendes, looking a lot more relaxed here than he did at his last roost, Viajante.

His menu here is simpler, a tempting tour d'horizon of current food obsessions, with its heart in America and some of Mendes's more outré tendencies on its sleeve. For as regular as many of the dishes sound – roasted short rib, for example, or chargrilled Iberico pork – these are fashion-plate versions, intricately worked to titivate jaded international palates.

Things start simply enough. Cornbread, fried chicken and doughnuts have become the holy trinity of contemporary casual dining. The Firehouse's bar-snack versions are right up there; the cornbread served in elegant fingers, with a silky chipotle-warmed butter, the fried chicken buttermilk-soft under a crisp, peppery crumb, and the doughnuts taking the beguiling form of mini-brioches stuffed with spiced crabmeat.

When Viajante opened, I admired Mendes's invention, while regretting his focus on such unappealing ingredients as chicken skin. But that was before it became a thing. I love it now, obviously. Here it appears as glazed sheets to reboot a conventional, and delicious, Caesar salad. Steak tartare is served Japanese-style, the components prettily arranged like paints on an artist's palette for self-assembly, with chipotle sauce to add heat.

We were just finishing our starters when the tree came down. My notes after that become patchy. I do remember, though, enjoying maple-glazed salmon, crowned with a big puff of salmon skin like a guilt-free pork scratching, and partnered with beets. Not so enjoyable was the other main course of chicken seemingly cooked sous-vide to leave it as pale and denatured as a TV dinner in space, and partnered with a slithery kale and bread pudding. Another side dish, sweet potato puréed with bourbon, was grim, like a vegetal zabaglione.

Things got back on track with desserts. The star was a frozen apple panna cotta with toasted meringue and a herb granita. The dessert list looks irresistible, not that many of the Firehouse's target audience will try it, judging by the twiglet-thighed honeys in micro-shorts who inhabit the dining room.

I returned for Sunday brunch expecting a homelier scene, but it's just the same twiglet-thighed honeys, this time with their toddlers. The food – brunch classics with a twist – is superb, though, and with most dishes from £8-£15, it's a more affordable option.

Whether it's an option open to all is another question. It was only by hissing 'I'm the person who had to be rescued from a tree' that I managed to get back in for brunch, only to find the place half-empty. Appropriate perhaps, that in keeping with its previous incarnation, the Firehouse seems to operate a strict no-civilians policy.

Food ****
Ambience *****
Service *****

1 Chiltern Street London W1 (020-7073 7676). Around £200 for dinner for two, including wine and service, or around £20 a head for brunch