2 Broke Girls, E4

Where would America be without its diners? Or for that matter, where would US culture be without them? Now here's another dramatic piece set in America's version of the greasy spoon, a sassily scripted sitcom by Whitney Cummings and Michael Patrick King, who created Sex and the City. Whereas SATC was set in Manhattan, 2 Broke Girls is located in New York City's less monied, but nowadays more groovy, borough of Brooklyn.

The set-up is very much of our times. Max Black (Kat Dennings) works two jobs to make ends meet: during the daytime, she is nanny to Brangelina, the twins of rich Manhattanites, then she works the evening shift as a waitress in a hip Williamsburg diner. Into the diner comes new waitress Caroline Channing, a Wharton School graduate and trust-fund recipient whose father has just fleeced every rich person in the city in a Ponzi scheme. Caroline was rejected by her so-called friends when she was left penniless and homeless after the family's Upper East Side property and her trust fund were seized by the feds. Now she has to work for a living, and of course doesn't have a clue about waiting tables.

It always amazes me that in the land of the PC, cardboard cut-out ethnic characterisation is considered OK

It's an age-old set-up, of course; two worlds collide and the inhabitants find they have more in common than that which divides them, and so it proves with Max and Caroline. After Max's cheating boyfriend is conveniently turfed out of the apartment when he makes a pass at Caroline (so setting up all sorts of scenarios), the rich girl moves in. Then she finds out that Max makes gorgeous cupcakes and plans a business deal - the series' USP - where they try jointly to earn $250,000 to set up a bakery in Manhattan and make their fortunes. At the end of last night's opening episode, they had $357 in the bank, and away the show goes.

The script is full of zingers and acerbic put-downs, most of them given to Max, a streetwise, take-no-prisoners hardass. When two hipsters wearing woollen hats were rude to her in the diner, she said: “I wear knitwear hats when it's cold outside. You wear knitwear hats because of Coldplay,” and when Caroline moved into the apartment and commented on its shabbiness, she said drily: “I babysit for a Manhattan socialite diva. Now I have a set.”

Dennings is bang-on as Kat, but Behrs made a slighter impact last night - although that changes as she gets more to do in later episodes, when her business savvy is indicative of a quick brain (and lip) of her own.

The funnies kept on coming, although I have some reservations. The minor roles are woefully underwritten, meaning that the timbre of 2 Broke Girls is entirely in the Max-Caroline relationship. That dynamic is rich (forgive the pun) territory to start with, but for longevity's sake other characters will have to be developed so they can play off them.

And the ethnic characters are one-dimensional going on racist; the diner's Korean owner, Bryce Lee's (Matthew Moy) use of English is constantly being corrected, and cashier Earl (Garrett Morris, pictured above) is in a twinkly-old-black-man-dispensing-wisdom role. It always amazes me that in the land of the PC, cardboard cut-out ethnic characterisation is considered OK. As for the Stephen Hawking joke about him struggling to do up his cufflinks - well I suspect no British sitcom writer would dare, unless his name was Ricky Gervais.

But overall 2 Broke Girls is smart and funny and I will - like most viewers, I suspect and unlike those who started out with New Girl, which covers some similar girl-in-the-wrong-place territory - stay with it.

• 2 Broke Girls continues on E4 each Wednesday