Two years ago her single "Bad Babysitter", about a night in with a neighbour's offspring, during which she gorges on junk food, performs oral sex on her boyfriend and makes sexual advances on the father of the house, propelled her to No 11 in the UK charts. Jarvis Cocker, William Orbit and Sarah Jessica Parker have since declared themselves fans. So why isn't she a household name?
"I've been wondering that myself," she says. "I'd say it's because I've always done things on my terms, putting music out on my own rather than signing it all away to a major label. Or it could be just because I swear a lot."
X-rated as her rhymes are, they provide a refreshing alternative to the increasingly blinkered and boorish attitudes peddled by mainstream hip-hop stars. Her modus operandi is "to attack with humour... I think most people get what I'm trying to do. It used to drive me nuts when they said I was the female Eminem but at least he's good with words and funny. There are worse people you could be compared to, like, say, Jessica Simpson. That would suck."
Her new electro-infused album My Machine, produced by the Madonna collaborator Jacques Lu Cont, imagines a dystopian future where children are named after advertising slogans and Princess Superstar, after selling her soul to a computer in a Faustian pact, is the only celebrity on earth. In typically saucy style, the single "My Coochie Coo", released this summer, found the rapper extolling the virtues of her nether regions, while "What Do You Want?" ("Nobody knows who won the Nobel prize, but everyone knows the colour of my eyes") examines our unquenchable thirst for stardom. "It's about the culture of celebrity gone out of control and ego gone mad," Kirchner reflects.
Despite the hype that accompanied "Bad Babysitter", even moderate success hasn't come overnight. "In the US, being a white, girl rapper is still a big deal. There's never really been one who's been successful. Blondie dabbled in it but it never really happened. The underground rap scene has been really supportive. I've collaborated with people like Kool Keith and they love what I do because I'm taking hip-hop somewhere else. But as far as mainstream hip-hop is concerned, they don't acknowledge me at all."
Kirchner, the daughter of a Sicilian-American mother and a Russian-Polish father, had a middle-class upbringing and a private-school education. Her musical heroes take in everyone from Salt 'n' Pepa and Public Enemy to Chrissie Hynde and David Bowie. She first heard hip-hop on a pirate radio station and was instantly captivated by the wordplay.
She won't reveal her age - "San't we just say 29 and call it a day?" - but confirms that she was born in Washington Heights in New York. "I only lived there until I was three," she says. "One of my earliest memories is sitting on a stool overlooking the city and being entranced by the buildings, lights, noise, everything. After that we lived on a farm for a while and then moved to the Philadelphia suburbs. I really hated it there."
At 17, Kirchner returned to New York where she enrolled at a college of performing arts. She learned to dance and act though in her spare time she played guitar and joined a series of indie-rock bands. The rhyming began as "a joke really. I just wanted to make my friends laugh. One of the first raps I wrote was 'I'm white and I'm from Pennsylvania/ I don't have no gold and I don't have a pager.' People laughed so much that I decided to put together a demo tape." The major labels quickly came calling but she self-financed and co-produced her first three albums Strictly Platinum, CEO and 2000's Last of the Great 20th Century Composers, and released them on her own imprint, A Big Rich Major Label.
It wasn't until her fourth album, Princess Superstar Is..., that Kirchner found a like-minded Berlin-based label in K7!, which would distribute her records abroad, allowing her finally to make her mark on the UK charts with "Bad Babysitter". The success came as a shock, she says, not least because 12- or 13-year-old girls would sing along to the X-rated lyrics.
"That was quite shocking. When I wrote that song I had adults in mind." She thinks about what she's just said. "Who am I trying to kid? I love it when I hear people singing my songs. Let them spread the Princess Superstar word. Soon there'll be no getting away from me and I really will be as big as Eminem."
The single 'Perfect' is out on 5 September on K7!; 'My Machine' on 12 SeptemberReuse content