A couple of years ago, I published a novel about the rise and fall of a great Anglo-Jewish restaurant and hotel business. As trade flourishes, the two partners find themselves craving acceptance beyond the confines of the Jewish community from which they sprang, and so they rewrite their menus. Accordingly, chicken soup becomes consommé de poulet. Because, of course, putting it in French makes it glamorous and refined, and if it's glamorous and refined it ain't too Jewish.

Here's the thing: it was a joke. Not the best joke in the world, perhaps, but a joke all the same. And yet, just a couple of years later, I am sitting in Six-13, Britain's 'first-ever kosher-fusion restaurant' - like we needed one - and there, listed among the starters, is chicken consommé. Apparently it's the same as chicken soup, only it costs £5 a bowl. Next time I attempt to make jokes about the pretensions of Anglo-Jewry, I'll have to aim a little lower.

Before the arrival of Six-13 (named after the 613 commandments the observant Jew must follow), if you had asked me to define kosher-fusion I'd have said it's what would happen if Vanessa Feltz and Jerry Seinfeld ever ended up in bed together. As far as the management is concerned, however, it simply means that religious Anglo-Jewry - the ones who keep kosher - should not be locked away in some mittel-European culinary ghetto of salt beef and lockshen pudding while the rest of the nation pleasures itself at the global larder. They, too, should have the right to eat crispy ginger and coriander pesto. Except, of course, if they happen to like salt beef and lockshen pudding because, significantly, both are on the menu here.

Regardless of the grand claims that Six-13 makes for its concept, its core audience seems to like it. The roads leading from Hendon to the sleek, modern premises on London's Wigmore Street must have been bumper to bumper with Volvos on the week night we visited. It was packed. I hadn't seen this many Jews in one place in London since my Bar Mitzvah.

As for the food, given the constraints it must work to, there's not much to kibitz* about - which is a shame, because it's what Jews do best in restaurants. As well as the obvious things such as no pork or shellfish, the most striking limitation on a kosher restaurant is that milk and meat must never be mixed. Those kosher restaurants that do use dairy products will serve only fish; Six-13 goes the other way, serving meat but no dairy. We went with Jonny, who keeps kosher, and his wife Sarah. Jonny took one look at the menu and said, 'Almost no one will be ordering the fish here. Fish they can eat at home. They'll all be eating the beef.' He was right. Platefuls of red meat were piling out of the kitchen as quickly as the waiters could schlep** them.

For my starter, I tried to order the pan-fried foie gras, but the waiter told me it was off. Actually, he said, it hadn't yet come on. The Beth Din, the rabbinical court that passes foodstuffs as kosher, had thrown a broigus*** and refused to approve their supplier of liver. He gave a big 'what can you do' shrug. Instead I went for the seared tuna with pickled vegetables, at £7.50. The fish had barely been on nodding terms with the heat and was, to all intents and purposes, a great, purple chunk of sashimi. That was fine by me. It was fresh and the pickled ginger on the side suitably sharp. Pat's grilled provençal vegetables with salsa verde (£5.50) was well executed. But the chicken soup - sorry, consommé - got the thumbs down from Jonny and Sarah: it was, they said, a rather polite affair. You could barely tell a chicken had died for it. In short, nothing like any of our mothers could make.

For our main courses we all had the meat. Here, as we had begun to suspect it would be, the fusion thing was suddenly forgotten. There is nothing controversial about steak and chips, or roast rack of lamb, or roast duck breast with pickled red cabbage. But they were all fine cuts of meat, despite the kosher law requiring flesh to be drained of blood before cooking. At an average of £18 a shot for each, though, they were damned expensive.

It was in the puddings that the absence of dairy really showed itself. My pavlova was crying out to be smothered in cream, Jonny's tarte tatin came with a scoop of very strange-tasting ice cream, and Pat's coconut rice pudding, clearly made with coconut milk, was simply odd. But that was OK, because finally we got to kibitz about them and that made us very happy.

Six-13 is rather less than it claims to be. It's a modern and expensive take on the kosher restaurant which proclaims innovation and yet does absolutely nothing that might frighten its target audience. And its target audience seems to love it.

*kibitz - like complaining, but with much more shrugging.
**schlep - carrying things around while kibitzing about it.
***broigus - an angry outburst, often occasioned by being asked to do too much schlepping.

• Six-13, 19 Wigmore Street, London W1 (020 7629 6133). Dinner for two, including wine and service, £95. Contact Jay Rayner on jay.rayner@observer.co.uk. His Day of Atonement is available from Amazon.co.uk