There are only a handful of French actors who have become household names outside their own country: Catherine Deneuve, Isabelle Huppert, Marion Cotillard, Gerard Depardieu and Juliette Binoche. It stands to Gallic reason that the last two in that short-list should be at public loggerheads. After Binoche won the best actress prize at Cannes in 2010, Depardieu sneered to one magazine: ''Please can you explain to me what the mystery of Juliette Binoche is supposed to be? I would really like to know why she's been esteemed for so many years. She has nothing - absolutely nothing.'' For her part, the woman known in France simply as La Binoche dismissed his insults as ''his problem''.
And so it seems to be, given her credit list. Binoche is only the second French female actor to win an Oscar (in 1996 for British director Anthony Minghella's The English Patient), and the only female actor to win the European grand slam of festival prizes, with best-actress awards in Berlin (The English Patient), Cannes (for the Iranian Abbas Kiarostami's Certified Copy in 2010) and Venice (for Three Colours: Blue by Polish director Krzysztof Kieslowski in 1993). She had triumphant theatrical outings in London and on Broadway, as well as in France, and even a dance piece titled in-i, devised with British choreographer Akram Khan, that toured 11 countries. There have been a lot of flops, too - often in illustrious company - but Binoche has never been one to stick to safe options.
We are here to discuss Elles, a film about student prostitutes directed by a young woman as yet unknown outside her native Poland, Malgorzata Szumowska. Binoche plays Anne, a journalist with Elle magazine who is researching the prostitutes' lives. She leads us through the story as a real journalist might do. When she was at acting school, Binoche knew someone who was working as a prostitute - ''I felt for her, but I didn't have any judgment because who am I to judge her?'' - but her only real research for this film was to watch a documentary about the two Polish students on whom the story is based.
''I decided not to prepare because, in a funny way, I wanted to be insecure. It gave me a sort of tension,'' she says. She made up many of Anne's questions herself. Was she shocked by anything she discovered? ''The addiction,'' she says crisply. ''The need to do it, the pleasure and need. Seeing sex as a drug.'' For one of the women in the documentary, she remembers, sex was like drinking.
''The body is part of a way of escaping something else - escaping an emotion, in a way.''
But Elles is as much about the widening fissures in Anne's own careful, comfortable, bourgeois life as it is about the girls. Anne has everything - rewarding job, Parisian house, successful husband, children - but everything is not, we realise, nearly enough. This is real Binoche territory: chewing up the familiar and spitting it out.
''We all need comfort,'' she says. ''But for a couple, of course, it has its dangers … Because of course we all want to live with desire, with passion, with evolution. When you are in a habit of things, can you survive if you don't lie to yourselves?''
She finds the corrosive effects of habit terrifying, she says. She has had a succession of long-term partners, including director Leos Carax and actor Benoit Magimel.
''I like to live in the present,'' she has said. ''I know this makes some people think I probably never cared, but I need my freedom and I need to keep moving.''
In art, she craves provocation, to be thrown off balance. She told film website Indiewire that she dreaded ''being sure of yourself'' and ''not working with intelligent people''. Things that don't scare her, on the other hand, include the masturbation scene in Elles.
This scene, which focuses entirely on her face in various stages of tension and cataclysm, had some of the anglophone critics in something of a lather when the film was first shown in Berlin. Not just because of its frankness, but because it ''manages the rare feat of making her look ugly'', to quote the British Daily Telegraph.
The irrelevance of this observation to Binoche's concerns as an actor - or, indeed, as a human being, judging by the odd assemblages of clothes she wears to interviews - illuminates what it is that makes her so remarkable. ''The body doesn't judge; it doesn't edit,'' she says. ''It goes into the experience of it … if you want to control your image, it's wrong. It's against life, in a way.''
One reason Binoche has had such a broad international career is that she pursues directors who interest her. After she called the Austrian maestro Michael Haneke, they went on to make Code Inconnu (2000) and Cache (2005), which the director later remade with an English-speaking cast as Funny Games.
Szumowska's script for Elles simply arrived on her desk, but she read it keenly because she had already been tipped off by an old comrade - Slavomir Idziak, the director of photography for Blue - that she would be the next big thing out of Poland.
Szumowska was more hesitant. ''We met and, of course, the first thing she said is, 'Oh, you have strong personality, a strong personality, we will not get along, I don't think so, there is going to be trouble!''' So did they fight? ''No. Actually, we got on very well. We are going to make another film together.''
Binoche is certainly a force of nature. Her relationships with other directors have been volatile. Louis Malle described Damage (1992), in which Binoche starred as a British Tory minister's much-younger lover, as the ''most difficult'' film he had made; she argued so fiercely with Claude Berri over Lucie Aubrac, the story of a French Resistance heroine, that she was replaced six weeks into the shoot, an experience she described as ''an earthquake''.
Even an interview with her can be rather alarming. Every now and then she lets rip with a raucous kookaburra laugh that is fabulous in itself but often triggered, disconcertingly, by amusing things only dogs and Juliette Binoche can hear.
The laugh seems of a piece, however, with her intensity. ''When I'm in the movie, I'm entirely in the movie. When I'm on the set, I'm 200 per cent there; when I'm at home, I'm 200 per cent at home,'' she says.
''I'm fully wherever I am, that's how I like to live my life.''
Unsurprisingly, she demands the same quality in a director. ''I want to feel it costs them something. They have to have the courage to face an aspect of themselves because I think art is fulfilled with your soul and being, not with ideas coming out of the head.''
An actor's relationship with the director is a kind of seduction, she says, a waltz of minds distinct from surface attraction or sex appeal. ''Seduction is functioning between child and its mother or father. It is part of the communication and movement between people,'' she says. ''I don't feel I have a natural sex appeal at all. I was never conscious of it. I felt the attraction I could give was the depth.''
Unlike many actors, she has no urge to become a director. ''My collaborations with directors are very intense and personal, so I don't feel [frustrated],'' she says. ''And you know, when I dance I don't need to act, when I act I don't need to paint and when I paint I don't need to dance.''
Painting is another of her pursuits. When she played an artist losing her sight in Les Amants du Pont-Neuf (1991), the paintings shown were her own. ''What I need is to express my passion for life … It's movement I'm interested in, the life in me, the life in humanity.''
If there was one project that brought this into sharp perspective, it was in-i, the dance piece she made with Khan. Dance is different from acting, she says, in that the dancer draws on a lifetime's muscular training to master and repeat the same movement thousands of times. But Binoche is not a dancer; she didn't have those muscles.
''So as an actor I was interested in starting with the emotion, starting with the feeling and then discovering what the gesture is. So it started off in a different way. I didn't have the perfection, I didn't have the muscle, I didn't have the core, but the fascination for me was: how do you make a movement with emotion? Working together was such an interesting dilemma and challenge.'' All that union of mind, body and spirit: it sounds draining, I say. ''I'm just interested. I want to know why I'm alive … it's like exploration, it's like someone being interested in a place and its history, digging into the earth and looking for it, searching. It's a passion.''
Is she wiser now in middle age - she is 48 - than the angelic young woman seduced by Daniel Day-Lewis in The Unbearable Lightness of Being, way back in 1988? ''I don't know about wise,'' she says. ''I know about wild!'' She laughs again, fit to raise the rafters. ''[Acting is] a crazy thing to do, but I just love it.''
Elles opens on Thursday.