In the weeks before the opening of their restaurant, Chris Galvin, the older of the two brothers whose name is above the door, had a recurring dream. 'It was a nightmare really, wasn't it?' says Jeff, his younger brother. Chris agrees that it was. 'We'd open the doors for the first time and nobody would come in. Ever! In this dream of mine the place just stayed deserted.'

Happily the nightmare was only that. From the moment in early September when the two chefs started cooking at Galvin, their wood-lined, slate-floored restaurant on London's Baker Street, the place has been mobbed. When they wrote their business plan, they worked out they needed to feed 40 people at lunch and 70 at dinner to break even. Every day they are doing at least 70 at lunch and 100 at dinner, and turning large numbers away. They receive 1,000 telephone inquiries a day. 'If somebody had told me that we'd have two girls in a back office simply answering the phones I'd have laughed at them,' Jeff says, but two girls to answer the phones is exactly what they have and by necessity. They have had to double their staff and are looking for more skilled cooks to work in the kitchen.

Though some in the industry questioned the wisdom of taking over the site - it had already proved a graveyard for a number of restaurants - the virtues of Galvin quickly became obvious. After years on the Michelin treadmill, turning out highly evolved and complex dishes, the brothers had decided to give it all up in favour of simple French classics done really well: steak tartare or duck confit, cassoulet or the best black pudding with the finest pommes purée. In short, comfort food for grown-ups, and at comforting prices. 'I can't imagine ever being miserable again,' wrote the man from the Times, after his first visit. 'At least not when I'm inside it.' The lady from the Independent also swooned. 'Starters were wonderfully prepared and presented ... mains too provoked gasps of pleasure.'

This critic can only agree.

Most of all, they made the business of opening and running a great restaurant look terribly simple. But behind this story of razor-sharp professionalism and great taste lies another one, which is anything but. Because, at the heart of their success, lies a tight relationship forged in adversity, a long way from the classy chatter and buzz of the dining room they can now call their own.

Chris and Jeff Galvin were born and raised in some poverty in Brentwood, Essex. 'When I was 15 our dad walked out on us, and we haven't seen him since,' says Chris, who is 47. 'I'm 12 years older than Jeff so in a way I became a father figure to him.' There is no mistaking them as a pair. Jeff may have thicker hair, and Chris may wear a few more miles on his face, but the same tight features are there. It is the end of a busy lunch service and we are sitting at a back table, just below the window through to the kitchen which allows the chefs to observe what's going on front of house. Jeff finishes off cooking the last of the dishes before joining us to share a plate of charcuterie and a whole vacherin cheese, which has been melted in its box to make an instant fondue. It is a cliché to say that close couples finish each other's sentences but with these two it's true. When one is eating the other talks.

Their mother, Kathy, was the pot washer at a local Brentwood restaurant called the Old Log. 'My mum loved the gossip at the Old Log,' says Chris. 'It was like a soap opera to her.' Then as now, dish-washing was not a well-paid job and Kathy had to work very long hours to provide for Chris, Jeff and their middle brother David. 'To be honest we were pretty much penniless,' Chris continues. 'The restaurant gave us food, it gave us drink, it gave us warmth.' Jeff agrees: 'A restaurant can be a fun place to be around when you're a kid. I used to play there during the summer holidays.' Chris admits that he regrets having had no further contact with their father. 'It would have been nice for him to acknowledge what we've managed to do,' he says. 'But Jeff says he doesn't remember him so it makes no difference to him.' They heard a rumour that he ran a café in Southend for a while, but know nothing more than that.

Certainly without his presence there was a real imperative to earn money as soon as they could and it seemed logical that their first jobs would be at the Old Log. When Chris was 15 he started washing dishes. By then there was a new sous chef. His name was Anthony Worrall Thompson.

'Chris was always very enthusiastic,' remembers Worrall Thompson. 'He used to come in to the kitchen after school during the week and at the weekend. The chef was on the verge of retiring so I started doing the food I liked, more modern food. Chris was really interested in that. It's funny how we both rose quite quickly and unexpectedly. He is technically a great chef. I think his food got a bit poncey at one point but now, at his new place, he is doing my style of food - real honest food at good prices. It's the best new restaurant I've been to for years.'

'He was a bit of a father figure to me,' Chris says. 'Taught me right from wrong.' He was also an inventive cook. The restaurant made its reputation serving the kind of classics ubiquitous to the Seventies: Sole Meunier, Blanquette de veau, Coq au vin. ('The kind of dishes we're doing now,' Chris says wryly.) Worrall Thompson was constantly trying to change things which infuriated the head chef, but intrigued the young pot washer. 'That taught me a lot,' says Chris.

And Chris was ready to learn. He'd always enjoyed cooking at school. Then Terence Conran opened a branch of Habitat in Romford Market. Wandering through it, Chris came across a copy of Cuisine Gourmand by the revered French chef Michel Guerard. 'That turned my life around. There was a whole new world in there.' On his wall, alongside the posters of George Best, he had pictures of French uber-chef Paul Bocuse. And so, when he finished school, he went to catering college and quickly won student of the year. When he was 12 Jeff followed Chris as pot washer at the Old Log and after that also went to catering college. 'It just seemed the thing to do,' he says, which is to say it seemed the only thing to do.

Both brothers continued their training in big hotels, Chris at the Ritz, Jeff at the Savoy (alongside Giorgio Locatelli and Marcus Wareing). And both would end up heading their own kitchens, but many times they also worked together. In the late Eighties and early Nineties they were in the kitchen at a country house hotel in Shropshire and later, in London, at L'Escargot. Jeff went on to work with Nico Ladenis, when Nico won his third Michelin star, and then joined Marco Pierre White. Chris worked for Worrall Thompson in New York and, launched the Orrery for Terence Conran. In 2000 Chris won his Michelin star. A year later Jeff won his star at L'Escargot where he was now head chef. Soon Chris was off to launch the Wolseley, for Chris Corbin and Jeremy King who had made such a success of the celebrity-haunted Ivy. 'It was too good an offer to turn down,' Chris says. At the Wolseley, which prided itself on serving sophisticated comfort food, the beginnings of the Galvin menu were already obvious. He served a terrific cassoulet.

But all the time the idea of running a restaurant together was bubbling under. 'Marco said he was going to buy a restaurant for both of us,' Chris says. Jeff says: 'Without talking about it we always knew that we'd do it, before we'd get too old.' Chris laughs. 'That's the optimist talking. I thought it would never happen.' But don't they argue? After all sibling relationships are notoriously difficult and top flight kitchens are highly pressured places. Famously, Michel and Albert Roux, who founded Le Gavroche together, weren't even talking to each other for a number of years. 'People would say we must argue,' says Jeff, 'but we don't.' Chris nods. 'Never had a cross word.' How come? 'It's about spending five years together in the kitchen,' Chris says. I ask them if they are proud of each other, they nod vigorously. What about any differences between them? They stare across the table at each other, as if studying their own reflections in the mirror. Chris says Jeff is a perfectionist, and will work endlessly to get one dish right, a legacy of his time spent in three-star kitchens. Jeff says Chris has a broader repertoire, a result of the longer culinary journey he has been on.

Chris also volunteers that he may be a bit more patient, and puts that down to the fact that he has four kids, aged between six and 22. Jeff's first child is due in April. Both Galvins credit their wives with being hugely tolerant of the 18-hour days they are currently working. At the moment, Chris gets to sleep around 2.30am and is up again at 5.30am. I ask how he is surviving. 'I simply don't know,' he says.

As to the kind of restaurant they would do together, that was never in doubt. 'I'm a bit of a lefty,' Chris says. 'My dad was a shop steward and that may be where I get it from. Anyway, it's about democratising food. We have to take it on the chin that it won't be fireworks on the plate but it will always be delicious.' Jeff does not believe the high gastronomic restaurants have had their day. 'There will always be five to eight of those in London doing the really ambitious food, but there's more and more room for what we're doing.'

It reflects a movement in Paris where young ambitious chefs have been leaving top flight kitchens to set up what are called 'bistrots modernes'. The Galvins call theirs 'Bistrot de Luxe' but it amounts to the same thing. One day, Chris watched an order go out of the kitchen and it was just a plate of smoked salmon and some oysters. He laughs. 'All we'd done was open the oysters and slice the salmon.' Jeff nods, 'Yeah, but it was great salmon and great oysters and that's down to our relationship with suppliers.' (The drive to simplicity is even reflected in the name. They didn't put an 's' on it, for fear of putting the apostrophe in the wrong place. In any case, they said, Galvin told you everything you needed to know.)

Before they launched they were given photographs and common aliases for all the top restaurant critics. 'I threw them away and told the staff no one gets treated any differently here.' And they stuck by that. An early visitor was the comedian and actor Alexander Armstrong, and Chris boasted to a friend at another table that they'd had their first celebrity. The friend pointed out the person Armstrong was dining with: Giles Coren, restaurant critic for the Times. 'I had no idea who he was,' Chris says.

To see the Galvin relationship in action I spend a lunch service with them. The plan is that there will always be a Galvin in the kitchen, though at the moment they are only allowing each other one day off a week so most days you get both. Today, Chris is at the pass while Jeff is on the meat and garnish station, working alongside the four other cooks. I ask them when they decided who would do what today. Jeff shrugs. 'We didn't. It just sort of happens.' Chris says, 'We just do what's needed really.'

When they opened, the menu was a collection of each chef's greatest hits: a lasagne of crab and a terrific pigeon pie with glazed chestnuts from Jeff's days at L'Escargot, that cassoulet from the Wolseley and a parmentier of oxtail and black pudding from the Orrery. Since then the menu has kept changing and one of the pleasures is seeing dishes turn up that haven't been witnessed in restaurant kitchens for years, many of them collected by Elizabeth David. Today her contribution is breast of lamb St Menehould, the lamb long braised, then covered in crumbs and butter, grilled and served with kidneys. I ask Chris, who has a huge collection of cookbooks, if I can see his copy of Elizabeth David: his edition of French Provincial Cooking is almost falling apart from use.

I watch as the two brothers cook, performing a precise dance down the narrow corridor from the stove to the pass and back again, so that you barely notice which Galvin is actually plating up the dishes. They call 'chef' to each other, and shout times on dishes, but mostly they do not need to speak at all. At one point Chris has put half the garnish - a stew of leeks to go with calves' liver - on one plate. Jeff arrives at the pass and, not noticing the first plate, puts the other half - carrot purée - on another. In some kitchens a cock-up like this would be the cue for fireworks, but not here. Neither Galvin says a word about the error. Chris swiftly moves his garnish over to Jeff's plate, and whips the empty plate over to the sink to be cleaned. 'Brotherly understanding,' Jeff says, when he looks up and notices me watching. Chris says nothing. He doesn't have to. In any case, a new order has just arrived. There's another dish that needs plating, and a very full dining room that needs feeding.

Sex or food?

We'd put both on the menu.

Comfort cooking with the Galvins

First, remove antlers ...

Daube of venison, with quince and chestnuts

serves 4

1kg shoulder of venison, sinew removed

500 ml red wine

250 ml port

3 cloves of garlic

1 stick of celery

1 onion

Sprig of thyme

2 litres veal stock (reduced by half)

50g trompette mushroom

1 quince

50g honey

60g butter

12 chestnuts (roasted & skinned)

chopped parsley

Marinate the venison in the alcohol with the diced vegetables and thyme. Leave for 24hrs. Drain and reserve liquid. In a very hot frying pan brown off the venison and vegetables. Boil the alcohol, then sieve.

Place the meat, alcohol and vegetables in a braising pan then pour in boiling veal stock, bring back to the boil, cover with tin foil and place in oven at 150°C. Braise for approx 2hrs or until meat is tender. Allow to cool in cooking liquor.

Pick out venison from the vegetables and reserve, then pass off liquid through a fine sieve. For the sauce reduce the cooking liquor until sauce consistency then whisk in a couple of knobs of cold butter. Peel and cut quince into wedges, place in pan with honey and sugar, cook until golden and tender. Warm the venison and chestnuts in the sauce, dress in a bowl plate, add the hot quince sprinkle with chopped parsley.

Baba au Rhum

makes 25

500g strong flour

pinch of salt

15g fresh yeast crumbled at room temp

8 eggs (lightly beaten together)

20g caster sugar

30g water room temp

250g melted butter

50g soaked raisins

Soaking liquor

500ml water

500g sugar

juice of one lemon

juice of one orange

50cl dark rum

1 vanilla pod split and scraped into liquid

Bring all of the above to the boil, allow to steep for one hour before passing for use.

Glaze

30g apricot jam boiled with a tbs of water

Sieve flour and salt together, then add yeast, eggs, sugar and water and mix to a dough. Cover with clingfilm and place in a warm place to double in size.

Remove clingfilm, knock air out of dough, pour melted butter and beat until silky. Add two thirds of the raisins. Pipe the mix two thirds of the way up a Dariole mould and put into a warm place until the dough is 1cm above the lip of the mould. Bake at 190°C for 18min; remove from oven. Cool. Allow to dry for eight hours before soaking. Bring soaking liquor to the boil and drop the babas in, rolling them to soak all over and become bloated. Drain. Bring glaze to the boil, and brush the babas, pour rum over and sprinkle on raisins.