Organic meat, wheatgrass, daikon pickles - it's fast food, but not as we know it. But do kids really want this healthy happy-meal option? Oliver Bennett visits Babes'n'Burgers to find out if they're lovin' it

You need a high concept in Hollywood film studios these days - and also, it seems, in London's increasingly competitive restaurant land. At the new Notting Hill restaurant Babes'n'Burgers, the high concept, not to mention the top line, is "fast-casual".

Say what? Well, fast-casual is an American notion. Word Spy - the internet's jargon site - dates the phrase's first usage back to 1995, since when it has become part of the US dine-scape. What it means is pepped-up, good-quality, fast food, served to a new kind of fashionable punter who wants a bit more than a mystery-meat burger and doesn't care too much about such flummery as table service.

Babes'n'Burgers fulfils the healthy food criteria as well as speed of service, and has added a nursery-style back room. It is organic as well as "fast-casual", and it's here to take on noodles, pizzas and other stalwarts of inter-generational eating. Proprietors William and Sam Sarne - who have a 17-month-old son, Saul - jokingly try to insist that the restaurant's name isn't about kids but more because William "is a babe". Whatever, Babes'n'Burgers is certainly child-friendly.

William and Sam look rather fast-casual themselves. William is the son of Tanya Sarne, of the fashion label Ghost. His dad Mike Sarne gave the world geezer pop in the early 1960s with such tracks as "Dodgy Lookin' Bird" and the classic "Come Outside", featuring the voice of Wendy Richard - now of EastEnders - before directing movies such as Myra Breckinridge.

Coming full circle, one of the backers of Babes'n'Burgers is Nabil Elouahabi, who plays Tariq in EastEnders. Another backer is Albert Clark, son of fashion designers Ossie Clark and Celia Birtwell. "It's coming from the Big Mac idea, but it's new generation," says William. And it'll play straight to the 12-stepping, gut-cleansing, lactose-and-wheat-eschewing W11 crowd.

Sam, meanwhile, was an art director at Saatchi & Saatchi: "I got all the people there detoxing," she says. Recently, while working in New York, Sam was impressed by the number of restaurants serving such delicacies as brown rice. On her return, she and William put their heads together. "I said, 'Organic fast food'," says William. "She tweaked the idea and said 'salads'." Boom: B'n'B was born. So was Saul.

The nursery room has pink easy-wipe banquettes and a magnetic steel wall so that creative offspring can write poetry with sticky letters. "There'll be a Saturday club for dads, who can talk while the children eat fish fingers and chicken fingers," says Sam. Only these chicken fingers are rolled in spelt flour and served with crudités and organic Maris Piper chips.

The main restaurant - or café, if you prefer - is basic banquette and table stuff, with a little face-height mirror for that Nighthawks effect, a fast-food counter and industrial spot-lighting to illuminate up to 50 diners. William has designed a heart-within-a-heart logo which is on the floor and menu. "It's my signature," he says.

The site had been a greasy spoon, run by a Greek-Cypriot man for 45 years, who has now sold up and left. Sam, William and Saul live upstairs. It is as organic as it can be, and they've applied for Soil Association certification and a drinks licence, so they can serve beer and Prosecco. But they're going to close the door at 10pm, so that passing drunks wanting takeaway chips can only order through a window.

Sam swears by detoxification, colonics and the Leslie Kenton diet that emphasises raw food: Kenton being the ex-journalist with an individualistic vision of the perfect diet, whose website provides lots of fun vision-babble about the "journey of the seed", and so forth. "I don't believe in Atkins, but I do believe in food combining," says Sam. Nevertheless, Babes'n' Burgers might do an Atkins burger; wherein your beef will come with daikon pickle and no bun. "We'll have goats' milk for the coffee," adds Sam, who gives Saul goats' milk formula. Wheatgrass will be grown on the shelf as the Sarnes swear by it, including Saul, who drinks it diluted, regularly. The little fellow must have the healthiest gut in London.

Salads - including a sprouting salad, and a soba-noodle job with wakame seaweed drizzled with hemp oil - is served in little boxes. There are burgers from £2.75 and dishes such as salt- and-pepper chilli squid. We try some of the dishes. The beefburger - made with organic beef from Wickham Manor Farm in Winchelsea, East Sussex - is successful and, vitally, looks just like a proper fast-food burger. The soba noodles, the Caesar salad, the sprout salad: all conform to Sam's idea that one could viably take food away after coming home too tired to cook, and still eat well.

They may be slightly talking up the concept at B'n'B, but the proof is in the organic lactose-free pudding, and one suspects that the idea is highly marketable, particularly since more conventional fast-food providers are currently losing out in a more demanding market. "We're not doing health food," says William, somewhat bafflingly. "It's not élitist. We're trying to improve our lives by working on the micro and taking those benefits into the macro."

William is into Kaizen, the Japanese credo of constant improvement that drove Wagamama. Indeed, with William's plans for a small chain, the fabled noodle bar could be this couple's inspiration. "If the formula were right - well, it's not a formula exactly," says William, "we should be able to turn it on to high streets." Great stuff. Just hold the miso enema.

Babes'n'Burgers, 275 Portobello Road, London W11, tel: 020 7727 4163. Open daily, 7am to midnight