Not many people know this, but deep in the backwoods of Roscommon, on an island in the middle of an impenetrable bog, there is an underground laboratory where every spring, a fresh crop of young Irish writers is produced. This captive breeding programme is the product of decades of secret research and genetic experimentation, in which the carcasses of Wilde, Yeats, Joyce et al are carved up, spiced with a few new tricks and reassembled in a variety of combinations.

The latest playwright to have popped off the end of this conveyor belt is Mark O’Rowe. He looks and sounds a lot like Conor McPherson, author of The Weir: both are small, thickset, bespectacled Dubliners, who go about their craft with a quiet intensity. Like McPherson, he is 33, prodigiously talented and a master of the monologue.

But here, the analogy begins to break down. Of all the new crop of Irish writers, O’Rowe is most his own man. You only have to hear a line or a phrase of his worldwide fringe hit, Howie the Rookie, to know you are in his particular grimy, vicious and yet mythic urban world of no-hoper hoods, chancers and eejits.

All his plays come from what American playwright Neil LaBute called his “big swirling tornadoes of beautiful words”. It feels sometimes as if you have stepped straight into Finnegans Wake. But Joyce never had O’Rowe’s narrative thump. Then again, Joyce didn’t grow up in Tallaght, a new city in all but name of mainly working-class estates plonked on the edge of south Dublin.

Tallaght, in all its malls and motorway glory, is there before us in the first scene of Intermission, O’Rowe’s sprawling first film - nothing less than a comic Dublin Short Cuts. A huge word-of-mouth hit in Ireland, it is already the highest-grossing Irish-funded film ever.

Colin Farrell, whom O’Rowe’s script tempted back from Hollywood, swaggers into a shopping centre coffee shop and chats up the waitress, his dark charm at full beam. You never quite know where or how you will meet “the one”, he tells her. “We could fall in love ... On the other hand, I might be just a thief.” And with that he breaks her nose with one sucker-punch and rips the takings from her till.

O’Rowe remembers the scene with an altar-boy-gone-bad smile. “The darker stories turn me on. I like the feeling that things can turn bad at any time,” he says. “I never sit down and deliberately plot a point of horror, but if I have a choice between a character being knocked down and killed in the next five minutes or falling in love, I’ll usually go for them being run over.” Nowhere did he display this capacity to undercut and surprise more than in Howie the Rookie, when the hero of one monologue becomes the tragic, hapless victim of the next.

In his play Crestfall, which premiered earlier this year, he went further and found himself at the centre of a storm of outrage. Irish playwrights traditionally do their shocking safely across the water, returning to Dublin fortified with admiring London notices. O’Rowe, however, chose to stage his most unremitting work at the Gate, the Bentley of Dublin theatres, which once a year or so sprinkles some broken glass into its programme of Pinters and classic revivals.

“Bestiality at the Gate” was the headline O’Rowe is most proud of. “It was worth doing it just for that,” he says. But the nature of the outrage - mainly sparked by a junkie prostitute who is hired to fellate a dog - surprised him. “The play is a massacre, basically; there is just so much violence against the women in it. But I had people coming up to me saying they didn’t like the way the dog was treated. I thought',What? It’s cruel that he didn’t get his blow job?’”

Faced with Dublin’s relative conservatism, Michael Colgan, the Gate’s director, wondered aloud if he could fill the theatre. Howie the Rookie had drawn dismal audiences considering it was returning home in glory from sell-out runs at London’s Bush Theatre and the Edinburgh festival. “We got rid of our geniuses - O’Casey, Beckett and Joyce - but we’re keeping Mark O’Rowe,” Colgan said.

O’Rowe, too, is rueful about the whole experience of how the Irish regard their own. “There is a certain oppressiveness, a feeling that there is a thumb trying to push you down. It may be in our minds, of course. I’ve never got a hammering really. But the excitement you have in London over a Martin McDonagh or a Conor McPherson bursting onto the scene wouldn’t really happen here. Conor once said that he would never open here, because if he did, his play wouldn’t have a chance of survival. He might have been exaggerating a bit, but I know what he means. Even great stuff isn’t celebrated in an open-hearted way.”

Intermission, on the other hand, is as open-hearted as it gets - and certainly the bunting is out for it in Ireland. It helps, of course, that it features the cream of Irish and Scottish acting talent: Shirley Henderson, Kelly Macdonald, a dopey Cillian Murphy and Colm Meaney in a magnificent turn as Colin Farrell’s comic nemesis, a maverick detective whose “only human virtue” is his passion for Enya and Celtic mysticism.

O’Rowe began writing at 24 “for something to do” after spending his youth acquiring an extensive knowledge of the bloodiest films he could find. His many hours poring over the back catalogue of Dario Argento movies isn’t immediately apparent in Intermission, but clearly they had an effect. “Video came out when I was about 13,” he says “So I grew up on video nasties, cannibal movies and kung-fu flicks - I Spit on Your Grave and all that stuff. Really we only watched them for the goryness of the special effects. Nightmare in a Damaged Brain was so chopped to pieces by the censors that we would have to sit there and imagine what happened in the cut-out bits. I suppose they got our brains going.”

All very admirable, but it may be a while yet before Chucky makes it to Irish school syllabuses.