Streep is not imperious, or as terrifying as the editor she played in The Devil Wears Prada. She speaks softly, has a flutey laugh and complains about the publicity-round attire of smart clothes and flawless make-up. Indeed, she reveals, exhausted after making seven films in two years, she is taking a break -- "enforced rest" she calls it -- though not before a broadside against male Hollywood executives for ignoring the success of woman-focused films.

Streep is the most nominated actor in Oscar history (her tally stands at 15 with two wins, the last for Sophie's Choice in 1983), famous for utterly inhabiting her roles, from the steely magazine chief of Prada to the mother of the baby snatched by a dingo, Lindy Chamberlain, in A Cry in the Dark, to a bitter divorcée in Kramer vs Kramer, to a capricious hippie mother in Mamma Mia! In her latest transformation she is Julia Child, the first popular American TV cook, in Nora Ephron's film Julie & Julia.

The film follows the real-life story of a food blogger, Julie Powell, as she attempts to cook all 524 recipes in Julia Child's classic tome Mastering the Art of French Cooking in 365 days, alongside the parallel story of Child in the 1950s as she masters the cordon bleu cookery that was the foundation of the book and her career.

The film is great fun: no violence, mostly happy relationships, and lots of buttery, glorious food. You cannot wait for Streep to be on screen, booming and tootling as Child, alongside Stanley Tucci as her husband Paul. When the action shifts to near present-day New York, you find your attention drifting to your pick 'n' mix.

Streep recalls growing up in New Jersey, coming home from school, "and my mother [Mary] having it [Child's show] on. My mother was not a cook. Her cookbook was Peg Bracken's I Hate to Cook Book."

She is still trying to lose the weight she gained on Julie & Julia, she roars. "The food was divine."

Did it improve Streep's cooking? "The vote at home is yes. I've learnt not to rush. I'm snobby about the equipment. The pan does matter. I got my stove recalibrated to correct the flames. I got my knives sharpened. I had to unlearn onion chopping."

Streep was recently described as an economist's dream: every project she has recently been associated with has generated big box office figures. "It's hilarious," she says, stroking her chin.

"I wish I could figure out a way to capitalise on that. I think it's a series of happy coincidences and also that there are more women in the hierarchy of movie-making and movie-financing and they are more interested and less afraid of making movies that appeal to other women."

But this is a well-worn trend now. Hasn't Hollywood woken up? "It's always a shock to the studio," Streep says with real firmness, "because men run the studios and live their own fantasies through them. It's harder for a man to jump inside a woman character's mind and imagine: 'This could happen to me' than it is for a woman to imagine herself as a male character."

But surely the profits count? "They see it and they understand that there is a market and it will make them an enormous amount of money, but we all respond to instinct and it's their inner boy that jumps up and goes: 'Yeah, I wanna see another GI Joe'."

A recent article speculated that Streep may be up for another Oscar nomination this year; a source said that the organisation had noted a dearth of strong female roles.

"Parts are rare," Streep says, "the amount of product is rare. It's a large machine that markets these films, that makes theatre [cinema] owners commit their theatres half a year in advance -- that's how it works. Are they gonna buy GI Joe or are they gonna buy Mamma Mia!?"

There are good roles for women, but the films rarely enter the mainstream, she says. "My actor friends are all lamenting a lack of material. People are very fearful of where to put the money, and that leads to a timidity. For the kids there are cattle-calls; they're rounded up like models, plucked out, put in a movie and they're done by 23."

She laughs ruefully about the possibility of another Oscar nomination. "I keep thinking I should get a good answer for that question." She's the most nominated? "Yes, I've lost it 13 times!"

Next, her voice features as Mrs Fox in Wes Anderson's animated adaptation of Roald Dahl's The Fantastic Mr Fox, which opens the Times BFI London Film Festival next month. "He's very demanding," Streep says of Anderson. "He hears everything, even a quasi-breath. It's almost like he's tasting, tasting, tasting . . . 'Right, that's enough salt'. It was more like working with a composer, like he was hearing music inside his head and you couldn't hear it."

Later in the year she appears in a postdivorce comedy, It's Complicated. The Norma Desmond role in the remake of Sunset Boulevard is still for the taking.

"Ooh, yes. It would be fun. But my friend Glenn [Close] really knocked it out of the park with that on Broadway so I think she'll have first shot." She smiles. "I think we have to be a little bit generous and spread it around. I've had a lot of work."

Streep disagrees that her roles have become lighter. "Prada wasn't fun to play; it was like I had mercury in my mouth. Before that I did Mother Courage on stage, which in your wildest dreams could not be described as comedy. I don't have a production company. I don't have anybody directing my career, it just depends on what scripts come. If I like them I do them."

So, what next? "Seven movies in two-and-a-half years," she says quietly. "I've never worked this hard ever." Is she exhausted?

"Yes. I'm feeling like I need a break. This is not the most fun part," she says indicating the hotel room. "The most fun part is making the movies, the prospect of selling three in a row is... harder. Selling has more to do with wardrobe and shoes and cleaning up and being presentable."

Has she ever considered giving up acting? "No," she says, snorting at the idea. "But I do need enforced rest in my career. When each of my children was born I took a year off. It's very nice to have time to live, gather experiences, watch other people."

Was turning 60 this year important? "To everyone else it was," Streep says, grimacing. "It was a big number.

"The biggest thing that happened was not to do with my age but my youngest [Louisa] graduating from high school and going off to college. I always said when she did I would do theatre, but I'm so kind of exhausted at the moment, the thought of doing a play puts me on a gurney."

If she did take on a role, she says, it would have to be a fresh character, "so as not to have someone say: 'Well, she wasn't as good as Dame somebody'". She laughs merrily, but her handlers are hovering, tapping watches. The "selling" must go on.

Julie & Julia is in cinemas now