Meet Desiree Akhavan, writer, director and star of Appropriate Behaviour

It starts well, with chemistry, latex and long, lusty looks - all the ingredients for a fantasy sexual adventure. But once the clothes are off the vibe quickly changes. The hot, sweaty blend of bodies that was hoped for fails to gel. Subtly and slowly, and without a single word spoken, a chill sets in. Desire seeps from the room as if there is a slow puncture somewhere, the atmosphere shifting from exciting to excruciating in one agonising take.

It's this scene which best demonstrates exactly why this indie picture has been feted as the work of an outstanding new voice all the way from here to Sundance (where it premièred in January). Iranian-American Akhavan is a film-maker who likes to unpick the rough seams of human relationships with grubby fingers.

"No one shows the messy grey areas," Akhavan says, sitting in the meeting room of a hip London members club. "And I'm really attracted to investigating ugliness in life - things that are uncomfortable, things that make your stomach churn. How you get there and how you get out of it? . . . I don't like the word awkward. It's funny because I don't see the sex scenes as awkward - but I find them to be, like, a misalignment of expectations."

Our failures to connect, in both big and small ways, are what interests the 31-year old Akhavan. Because, she reckons it is something that occurs in almost all relationships at one point or another. "That happens so much in life, where you think you're on the same page, or you are on the same page, and then someone slips off, and you just go a different direction. That to me is, like, the essence of most relationships in my life. That sometimes we are walking on the same path, and sometimes we go apart. And the friendships that I've had that have lasted over a decade, we've inevitably gone apart for a while and then come back together and been on the same page, and gone apart. . . It's infuriating to me that most films just show relationships and characters as good or bad, positive or negative. And the films that I gravitate towards and that I have an emotional experience with really delve beneath the surface, and go for it with nuanced portrayal of good intentions and bad results."

Akhavan wrote, directed and starred in Appropriate Behaviour which is, though fictional, firmly based on her own experiences as a bisexual, middle-class 2nd generation Iranian American, frittering away her twenties in Brooklyn warehouse parties and coffee-shops in a haze of dead-end jobs and failed romances. In the film, we see her fail to own up to living with a woman to her strict Iranian parents, fail to connect with the hipster pre-occupations of the white middle-class American experience that surrounds her, and struggle to reconcile how she is with how she wants to be. Browsing optimistically in a high-end lingerie boutique after her break-up, she tells the sales woman she is looking for "the grown-up underwear of a woman in charge of her sexuality and not afraid of change."

Akhavan's jaundiced view of the millennial experience aligns her with similarly disaffected female voices who have emerged from the Brooklyn creative scene. But though she played a small role in the latest series of Girls, she bristles slightly that she's been so readily labelled the Iranian, bisexual Lena Dunham.

"It's a silent implication that there is room for one woman whose work can be monetised on that level," she says. "And you can have that level of success. . . I understand why people do it. I sometimes resent it, sometimes appreciate it. I feel really mixed about it. I'm not livid. I think it's sexist, yeah. I think it's lazy, and that it sends a really negative message to readers. But at the same time I get it, and it makes sense."

Like Dunham, Akhavan takes a first-person approach to storytelling, seeking to convey not just a narrative but a distinctive world-view. Appropriate Behaviour's subject is the inherent nature of its creator. For the audience, this provides an extra frisson of authenticity to the film. But it must be tricky to skirt so close to real-life detail, without pissing people off.

"It's a fine line," she admits. "And my family - we've all had practice with this, because a lot of my work is of this nature. I really try to be respectful, and I think a lot about that. I want to be respectful. And that goes into wanting nuance and wanting to not be one-note with anyone. I think that for the most part, all characters are understandable, and that you kind of get where they're coming from. When it comes to my family, the parents (in the film) are not very much like my parents. My parents are actually really warm. . ."

The character of the brother, a doctor who fulfils all parental expectations while Shirin flounders, is truer to life, she says.

"The brother is very much my brother. And my brother loves that, he thinks it's so funny. He thinks his lines are the funniest, he thinks his character is the best. . . We're very close. And I knew that he wouldn't be offended, and that it was an homage to him and like, how much I love our mean banter. I think you just have to be fair and everyone picks for themselves what's fair and unfair. And the things about the film - there are aspects that are true to my life, and many that are made up. And I know the difference. I find that line for myself."

Her own parents were traditional when she was growing up, though they've adapted a great deal since moving to America.

"They're not religious, but they were quite traditional in ways. And they became less so the older I've become and the more years that they've spent in America. They have progressively had to form this new identity, and America just keeps seeping into their skin with each year that passes. We grew up with a very strict division between them and us, and having, like, a very proper code of conduct. And that's really eased up over the years."

She never hid her sexuality from them, but coming out officially as bisexual wasn't easy. With time, however, they've proved themselves to be impeccably accepting.

"They've changed completely as well since I've come out," she says, characterising the choice as "Do you not want a child, or do you want to keep your relationship with your child? Those are your two options. There's nothing in-between. So you get on board or you cut it off. I think they considered for a while cutting it off, and realised that they couldn't do that."

Directing other actors and crew in something that is so much her story was the easy part of this whole process, she says.

"The fact that it's starring me, written by me, directed by me, made me really eager to have other voices in the room. So I was very happy to let go of control where I could. . . But I'm a thorough chooser of my collaborators. I really don't like working with people who are assholes. . . I would rather be comfortable in a situation and be able to bring out the best of someone's ability, than work with someone who technically has done more superior things or has a better reputation or better agent or whatever, if we can't communicate. My editor, my cinematographer and my producer are all very talented people so it was very easy to let go and say ok, you make a choice."

Appropriate Behaviour, by Peccadillo Pictures, is in cinemas now.