25 Catherine Street, London WC2 (020 7240 2078). Meal for two, including wine and service, £60

You don't have to be Jewish to like Mishkin's, but it probably helps. It gives you the right to kvetch about all the things that aren't as you think they should be. Though, of course, you need to be the right kind of Jew, which is to say only Jew-ish. Mishkin's, the latest venture from the sassy team behind Polpo and Spuntino among others, bills itself as a "kind of Jewish deli with cocktails". Given that my brethren are famous non-drinkers – I am such a bad Jew – this is a little like setting up a lingerie concession in a nunnery. Actually, it's nothing like that, but you get my point. If you're searching for something echt, to satisfy the frummers, you've come to the wrong place. This is a Jewish deli by way of New York, as imagined by a bunch of non-Jews. Kosher it ain't.

Prime among those non-Jews is Russell Norman, who used to work for the Caprice group – until he decided he never wanted to wear a suit again. When he announced that he and his business partner would be launching Mishkin's I insisted we meet so I could give him some pointers. I know. Shameless, isn't it? We sat down together over a few plates at Polpetto, his Italian above the French House in Soho, a meal I paid for. Norman looked baffled by my insistence that I lunch him in his own gaff but, as I said, had I done otherwise I could not have reported upon what was said.

For example, I told him that, when serving the salt beef, they had to ask the diner whether they wanted fat on or fat off. Fat is where the flavour is; if it's too lean it can be dry. We talked about chopped liver. He bid me try some of Polpetto's chicken-liver pâté. I told him it was lovely, a thing of beauty, but for Jewish chopped liver it was too wet, too loose. I said chrain, the killer condiment that mixes beetroot and horseradish, should be on the menu. But then I checked myself: at play here were my own particular cultural reference points. My shiksa wife thinks my love of the Jewish Ashkenazi staples she considers awful is some ancient weirdness, buried deep in the mitochondrial DNA, much as my love handles are still unnecessarily engineered for fearsome winters on the Russian steppe, on the run from the Cossacks. She might have a point.

So what of Mishkin's? The place looks lovely: there is the faux-30s frontage with half-net curtains, a U-shaped counter, wood-slatted walls, and American diner-style booths. The latter is key. This is a restaurant established by cosmopolitan types with a love for old-school New York delis – prime among them Katz's on Houston – and who wanted a bit of that here. The service, by the familiar inked and bed-headed crowd the restaurant group has made its own, is deft and encouraging. As is some of the food: the chopped liver is bang on. Just like my mama used to make: deep and earthy and dangerous. I liked the pickled herring on a bed of minced beetroot, and the chips and onion rings are the real deal. They serve Big Apple (all pork) hot dogs, which are a wonder.

But what of the main meats? First, the big positive. They do ask if you want your salt beef with fat on or fat off. It tastes right. But it is either being overcooked or allowed to stand for too long, because it is crumbling unto shreds like pulled pork. It needs to be served in slices. The pastrami in the Reuben sandwich (£9) – alongside Russian dressing, sauerkraut and Swiss cheese – is sliced far too thin. Anybody who has visited Katz's will find the sandwiches here disappointing. The Mishkin's crew need to (re)visit the Brass Rail in Selfridges, where they cut proper thick slices. Plus, they serve meat platters which Mishkin's doesn't. I could go on: no chrain, no garlicky new green pickles, and how could they have run out of chicken soup the day I went? How?

But for all that, I love Mishkin's. I love that anyone has bothered. And on a cold winter's day, with the windows steaming up, and the room full of noise and clatter it feels right. I can guarantee I will return and keep returning. I will kvetch. And then I will order another Reuben sandwich. You know, just to be sure.

Email Jay at jay.rayner@observer.co.uk or visit theguardian.com/profile/jayrayner for all his reviews in one place