Nora Ephron

Nora Ephron's new film about the joys of cooking slips down as easily as chocolate souffle, precision-baked to satisfy the appetite of the mainstream American female cinemagoer. There are laughs, there are tears. There are lots of lovely fats and carbs, safely out of reach on the screen. There is Meryl Streep, Ephron's favourite actor, chewing up the scenery as the daffy 60s TV chef, Julia Child. There is Amy Adams, cute as a button as Julie Powell, who baked and blogged her way through Child's Mastering the Art of French Cooking and then wrote a book about it. There are two dishy, endlessly helpful husbands. It's warm, sweet, unchallenging.

1. Save for one short scene in a bar. Julie has had a bust-up with her husband. "I'm a bitch," she wails to a friend. The friend says nothing. Julie is wounded. "You really think I'm a bitch?" "Well, sure," says the friend. "But so am I."

It's a tart little line, and a small shock amid all the fluff. Did Ephron hesitate before including it? Not at all, she says. She crosses her legs. She is immaculately arranged on an armchair at Claridge's in London, dressed top-to-toe in black and charcoal, elegant as a Faber-Castell pencil and nearly as thin. Now 68 (though she could pass for 15 years younger), Ephron is two parts Chrissie Hynde to one part Bob Dylan. But back to her script: does she think all women are bitches?

She fixes me with wide eyes. "Well, is it not true of you?" Sometimes, sure. "Well, it's true of you and me, so it must be true of all women, mustn't it?" Yikes. Must it? In the film, Julie vows to try and be more like Julia: game, saintly, kind. Ephron thinks. "Well, yes, and I have an occasional friend who would never, ever . . . who I think is just great all the time." She sits forward. "But most women are, sort of. I think that's the dirty little secret about all women. And they think nobody knows it about them."

And she thinks this is more so today? Julie's friends, almost to a woman, are money-grabbing monsters, not just prone to bitchiness but fuelling their careers by means of it. "I don't know. I mean, my mother was not anyone to generalise from." Phoebe Ephron was a studio screenwriter and an alcoholic, as was her husband, Henry. Partly, Ephron thinks, modern bitchiness is a time-management issue: "These days most women have jobs that last way too long. A lot of people in New York barely have time to get laid." A pause. "But I certainly think that, for quite a while, it has been true of women."

The $15 white plastic table

Ephron has built a career out of spilling secrets – hers and other women's. At 22, working as a researcher on Newsweek, she wrote a spoof of the New York Post. The first boss who noticed it considered legal action; the second thought it so spot-on she hired her. In her early 30s, she wrote an article for Esquire headlined A Few Words About Breasts, laying bare the pain of being flat-chested ("'I want to buy a bra,' I said to my mother one night. 'What for?' she said"). Her bestselling novel Heartburn, later made into a film starring Streep, told the world how it felt to have your husband leave when you are seven months pregnant with your second child. In real life, that husband was Watergate journalist Carl Bernstein, and the other woman was Margaret Jay. Which perhaps explains why, in the years that followed, Ephron took great pleasure in telling anyone who cared – and some who didn't – the identity of Bernstein's Deep Throat.

When she turned to screenwriting, Ephron repeated the trick. First came Silkwood in 1983, again starring Streep, as a nuclear worker and whistleblower. In 1989, when she was working on the script for When Harry Met Sally, director Rob Reiner challenged her to tell him an awful truth about women he didn't know. Sometimes we fake orgasm, she said. Not with me, scoffed Reiner. Ephron insisted. When the famous Meg Ryan-Billy Crystal deli scene was first screened, Reiner reported that the women were in fits, while the men sat in silence.

Since 1989, Ephron has been married to Nicholas Pileggi, who wrote Goodfellas and Casino. She's a grown-up and has learnt how to make a marriage work. "I always remember that I once had a fight with my first husband over whether we should buy a small white plastic table that cost $15. That is just an unimaginable conversation for me now. You can't make your marriage about something like that. If a person wants something like that, they should buy it." Perhaps it was really a fight about something else? "Whatever it's about – be it control or money – it's not worth a second of your life in a marriage."

She says her husband is "definitely a nicer person than I am". And it's striking that in her recent films the men are mostly decent and easy, the women more complex. Perhaps this has made men of less interest to her: Julie & Julia is in no sense a romcom; its male/female relations are just a pleasant background noise. But in fact, when you examine her back catalogue more closely, Ephron has always written less about relationships, and more about the differences between the sexes. In Sleepless in Seattle and You've Got Mail, her lovers spend almost the entire film apart, chewing the fat with same-gender friends and family. Harry and Sally riff off each other, and rarely connect.

Bitches or not, women are what Ephron wants to write about. In 1996, she delivered a speech to students graduating from Wellesley, the Ivy League single-sex college she attended in the 60s. It was a stinging warning that they should not imagine the world was a fairer place: "It's just as hard to make a movie about women as it ever was." When she was inducted into the Academy of Achievement in 2007, Ephron said she took up directing because "90% of the men directing movies have no interest in women in any real way, except as girlfriends or wives. They don't really want to make movies about them, and they don't."

But Julie & Julia is also a film about food. Ephron says that Child "found God when she went to the cordon bleu cooking school in Paris". It's an obsession for her, too. She goes into great detail about a lunch at the River Cafe in London the day before: "A simple thing of pasta with crab, just you couldn't believe it. One of the things I just love in London is how much they love the salt shaker. You never have to salt your food. And then we ordered almost all the desserts and ate them all." When she was starting out in New York, she says, being able to rustle up a decent boeuf bourguignon was absolutely essential.

In the end, though, what drives Julie & Julia is not the dynamic between women and men, or women and women, or even women and food: it's about two women and their book deals. All the flirting, the coy negotiating, is directed at unreliable agents and hard-to-get editors. The final frame, traditionally reserved for the big kiss, sees one of our heroines receive the first copy of her book.

Ephron points out the differences between the two women. "Julie was much more ambitious. Julia wanted to do something that interested her. And then she decided she would teach, and then she decided she would write a book, and then it was published. And never ever did she dream: I am going to be famous. With Julie, from the very beginning she had the ambition to become a successful writer – and a famous one, in that those two thoughts often overlap."

'Endless amounts of drivel'

Ephron says she empathises more with the younger woman. And it's true that she is highly driven, partly through necessity (she raised her two sons almost single-handedly), partly by design. She says she didn't want to be "just" a mother, and thinks we're now in an age of "complete parental insanity . . . the whole idea of having a career is that you should not have to go to meaningless chess matches week after week". Her drive is also hereditary. "Everything is copy," her mother told her, and it's something Ephron has repeated to herself, and to virtually every interviewer, ever since.

But is she really more a Julie than a Julia? Yes, she blogs – but for the Huffington Post, and on politics or theatre. The sort of blog Powell wrote would be anathema: "It's endless amounts of drivel coming out of your mouth. You would find yourself having completely idiotic thoughts in order to have something to write about." She doesn't tweet, and is sceptical about new technology ("Men own the internet: it's another world that's male").

Julia, on the other hand, is "the epitome of buckle down, never apologise, get on with it. We'd all like to be like that." Even today? Ephron takes a sip of Diet Coke. "No, I think most people aspire towards self-knowledge. And I don't think Julia Child was interested in self-knowledge. I do think there is a moment in life where you kind of have to do what Julia did, which is pull up your socks. I'm a big believer in that. And in denial, which is the opposite of self-knowledge."

Denial about what, I wonder: the facts of one's life, death? She smiles. "Oh, yes, absolutely. Those are good. I just don't think you can go through life savouring all the defeats. And basking in the sadness. I think you've got to be completely unrealistically Polyanna-ish at all times. I do." Certainly, this seems to have worked for her: if everything is copy, even tragedy can eventually work in your favour.

But if everything is copy, it doesn't necessarily follow that Ephron writes only from her own experience. This is something she has pointed out herself: in the preface to the most recent edition of Heartburn, she complains with some heat about the tendency to describe women's novels as "thinly disguised", while Philip Roth and John Updike are free to cannibalise their lives without exciting comment.

What makes Ephron such a successful screenwriter is her ability to inhabit other people's voices: scatty Meg Ryan, soulful Tom Hanks, lewd Billy Crystal, even randy Jack Nicholson (who played Bernstein in Heartburn). She is not like any of them. She doesn't even bear much obvious resemblance to the confessional writer Nora Ephron, whose admissions of ineptitude many women will have smiled in recognition at – just as they will laugh with Streep's Child when she drops a pancake on live TV, and then scoops it back into the pan with a merry "Who's to know?"

It's almost impossible to imagine the enormously polished woman in front of me ever being anything less than in total control. That, then, might be Ephron's own little secret. She is not everywoman. She is just rather brilliant at imagining how that might feel.