Whenever Helen Mirren's in need of a little pick-me-up, she searches out a slice or two of eggy bread. "My mother used to make it. Oh, it's amazing," she says, a wistful look in her eye as she pictures the naughty treat.

Fried carbs might not be the first snack that comes to mind when you think of the Academy Award winner but, she states, she "eats to live - I don't live to eat". And she loves food, particularly "fuel-type food, like mashed potatoes and fried bread".

Today, the 69-year-old is looking healthy, trim and elegant in a fitted berry red dress and heels. While you sense the Dame doesn't suffer fools, she radiates a down-to-earth warmth.

For instance, on hearing that her co-star in The Hundred-Foot Journey, Manish Dayal, had preconceived ideas of what she'd be like before meeting her, only to realise later that they actually share the same "dirty sense of humour", she starts laughing heartily. "I'd admit to that, yes."

"He's an absolute charmer, isn't he?" she says of the 31-year-old, who starred in teen series 90210 before being plucked by the movie's producers, Steven Spielberg and Oprah Winfrey, to play the lead in the big-screen adaptation of the bestselling novel.

Despite almost 50 years in the business and over 100 credits to her name, Mirren confesses she too couldn't believe it when Spielberg rang.

"It was that classic phone call of, 'It's Steven Spielberg on the line for you'. And whenever an actor is lucky enough to receive that phone call, you never believe it and think someone's having you on," says Mirren, who began her career as Cleopatra at the National Youth Theatre, earned a legion of fans as DCI Jane Tennison in the Nineties TV series Prime Suspect and won an Oscar for her title role in The Queen in 2007.

The Hundred-Foot Journey follows Hassan (Dayal), a culinary ingenue with the gastronomic equivalent of perfect pitch, and his family, led by Papa (Om Puri), as they move to a quaint village in the South of France with the plan of opening an Indian restaurant.

They're undeterred by the fact a Michelin-starred eatery stands just 100ft across from theirs, but underestimate the lengths the proprietor of the establishment, Madame Mallory (Mirren), will go to, in her attempts to close the gaudy restaurant. But even she can't deny Hassan's talent, and ultimately helps him on a journey that brings the warring factions together.

"I thought it was a charming story and loved the fact it was going to be shot in the South of France. I've always secretly wanted to be a French actress and I thought it would be an opportunity to pretend to be that," says Mirren, who was brought up in Essex to a British mother and Russian father, and lived in Paris as young woman, when she toured the world as part of the renowned director Peter Brook's theatre company.

On this project, she's directed by Lasse Hallstrom, the man who helmed Chocolat and The Cider House Rules, and who encourages improvisation.

"He warned me at the start of the shoot that he'll probably change things around and ask me to improvise," says Mirren. "He said, 'I like to keep things loose', and it was very true. He'd get an idea and suddenly go for it, so you felt you were never in a prepared rut that you had to follow. Sometimes that was frightening, because you felt wrong-footed, but it was always exciting."

There are wonderful moments in the movie, not least a scene in which Madame Mallory berates one of her chefs for allowing a limp asparagus to be served and then produces the offending item from a napkin. Their attitude towards food should be akin to a passionate affair she reminds her staff.

Mirren reveals there was time when she felt the same way about acting, "but I really don't so much any more," she reflects.

"I love my profession, don't get me wrong, and I'm very committed. But I'm not obsessed the way I used to be, especially as a very young actress. It was a church for me, my religion."

Ahead of filming, she met with an English woman who runs "a small but wonderful restaurant" in a French village. "It was important to meet these people, to understand the level of commitment they make. It's a 24-hour, seven days a week commitment, truly a life's commitment to be an owner of a restaurant or small hotel in that way," she says.

"And to realise what very forceful people they are, because these restaurateurs and chefs, they're artists, They live, breathe, think about their work. Like great painters, writers and hopefully great actors."

Mirren might play a woman who can detect whether someone has the potential to become a great chef with one bite of an omelette, but she wouldn't consider herself quite in that bracket in real life.

"I do incredible baked beans on toast, marmalade on toast, cheese on toast," she confides, grinning. "I love food and love to eat but I've never been a great cook."

She has her moments though. "Occasionally I'll cook something that's fabulous, but then forget how I did it because I make it up as I go along."

Her husband, the director Taylor Hackford, who she married in 1997, isn't much better. "He's very good at cooking pasta, in the sense of knowing when to get it out of the water, which is an art form, but neither of us are great chefs."

That would suggest the time they spend in Puglia, southern Italy, isn't spent in the kitchen. Although they have houses in the UK and US, Mirren considers their Italian home a haven, somewhere she can be herself, even if she isn't entirely anonymous when she goes out.

"I am known as 'The Actress' there, 'l'attrice', and that's all they call me," she says, smiling. "'We saw the actress in the restaurant', 'We saw the actress in the supermarket', but at the same time, it's southern Italy, so they're incredibly hospitable and welcoming."

It will be a while before she can revisit this retreat as she's about to begin shooting her next movie, Eye In The Sky. "It's about drone warfare and is as different as you can imagine from this movie," says Mirren, who will be playing a military commander.

And it will need to go some way to beat the atmosphere on set for The Hundred-Foot Journey.

"It was a very happy film and it felt like a real family making this movie. It's lovely when it happens like that," she says. "With the big movie stars, it's very hard to get that feeling going, because they've done so much, they've seen so much, they're so self-defensive and protected, they find it hard to be natural and easy.

"But with this sort of movie, people are just more relaxed."

EXTRA TIME - BEHIND THE SCENES

:: The film is based on the 2010 book written by Richard Morais and published in 28 countries. Producer Juliet Blake read an advance copy and secured the screen rights.

:: DreamWorks and Harpo were soon on board, with Steven Spielberg and Oprah Winfrey joining Blake as producers. It marked the first time Spielberg and Winfrey had worked together since 1985's The Colour Purple.

:: Hassan's love interest Marguerite is played by a newcomer, French-Canadian actress Charlotte Le Bon, after Steven Spielberg spotted her on a French variety programme.

:: Much of the film was shot in Saint-Antonin-Noble-Val. The town's farmers' market was used for pivotal scenes, with many of the vendors appearing as extras.

:: The property used for the Indian restaurant was actually a few miles from Saint-Antonin. Production created a road, fake stone wall and a false front exterior for Madame Mallory's restaurant. The rest was done in post-production to make it look like the buildings were opposite each other.

:: The Hundred-Foot Journey is in cinemas now