The world is fascinated by Angelina Jolie. Her beauty. Her husband. Her international brigade of kids. Now she's back with a reminder of what she does when she's not playing mom (actually, hang on a minute, she is playing mom). In Clint Eastwood's Oscar-tipped Changeling, she takes on the role of the mother of a missing boy. Michael Dwyermeets the woman who once kissed him in front of 750 people

THE LAST TIME we met, Angelina Jolie kissed me in front of 750 people. It was just a chaste peck on the cheek when I was introducing her on stage at the Irish premiere of Alexander, but friends who were there talked about it for days, wishing they could be so lucky.

I mentioned this when I met her again in London last Monday afternoon.

Jolie looked very convincing when she claimed to remember the kiss, but then, she is an Oscar-winning actress. She was 25 when she was voted best supporting actress for Girl, Interruptedin 2000, and she looks certain to be nominated as best actress in January for Changeling, the masterly new drama directed by Clint Eastwood, which features her most outstanding performance to date.

It opens in 1928 Los Angeles, introducing her character, Christine Collins, as the caring single mother of nine-year-old son Walter. He disappears, and five months later she's told he has been found in Illinois. When she meets the boy, she immediately realises he is not Walter. That is just the beginning of a fascinating scenario that expands to address a range of themes, some deeply troubling and just as pertinent in the present day.

The final revelation is that the film is based on fact, affirming the adage about truth being stranger than fiction.

"If it wasn't true, I can imagine people saying this couldn't possibly have happened," Jolie says. "When we got the script, they had Xeroxed the front pages from the Los Angeles Timesand other papers covering the case, so while you were reading the script, you could just flip over and there were all the actual pictures of her holding her son. As it unfolded, you were constantly reminded that it was fact."

Stories also abound about Angelina Jolie - and some of them are true. There is a media obsession with her and her relationship with Brad Pitt. She was heavily pregnant with their twins when she was at Cannes in May, and photographers pursued her everywhere. Then there were reports that she had given birth even before the twins were born.

She laughs and just shrugs when I raise that. "It's a strange thing when you're pregnant because I was just like every mom," she says. "I was sitting there thinking that I just want my babies to be healthy and praying that they wouldn't be born premature. That's all I was focused on, and I didn't want any more pressure."

Our conversation repeatedly returns to the subject of her children, and Jolie comes across as thoughtful and grounded, in marked contrast to her media image as a wild child herself when she was married to actors Jonny Lee Miller and Billy Bob Thornton.

"I can't really focus on what people say about me because it would get in the way of my work," she says. "I live at home with six children and I'm a mom. That's what I live with every day. My job allows me to do some good work and to draw attention to other areas. When I first started travelling with the United Nations, I did it because I felt I didn't know enough about the world around me and I felt a responsibility as an individual to educate myself.

"Then, as I travelled and learned a lot, I realised that there was so much that needed to be put out there in public. I was pleased to have something of value to speak of, something that I thought was important. I believe anyone can do as much good as they want to do, as long as they believe in it. I don't have any answers, but I hope I'm posing the right questions."

Some years ago she said acting was a form of therapy, but she plans to be acting less and less in the future. "You know, I'm all right now. I have needed it in the past to help me to express things and to learn things, but I now have a lot of children who teach me things every day. I need film less and I'm more needed at home. I haven't worked for a year. I'll work for a few months on my next film and then I'll take at least another year off."

As a mother, she was reluctant to the play the mother of a missing child in Changeling. "I couldn't put down the script when I got it," she says. "But I said no because it was too upsetting. Then, as I found myself telling more and more people about what it dealt with, I felt I should do it. I think anyone can relate to loss, if somebody they loved is taken from them for any reason. But being a mother certainly helped me as an actress in that role. Every time I used the word 'son' was very emotional for me. There's something about a child that makes you feel so responsible for their life."

After the end of each day's shooting, she was glad to go home and "just be silly and goofy with the kids", she says. "I was so relieved to step away from this role. I had my kids there when I had a break for lunch and I was just so happy that I knew where they were and that they were safe. During the film I got pregnant, so by the end of it, I was 100 per cent focused on babies."

Jolie is charming and gracious in person, and the only time she sidesteps a question is when I ask about her Oscar prospects for Changeling. "You know, I'm just thrilled that I didn't fail at my job, that I did okay and that I didn't let the team down," she says. "When you work on something that's about somebody you respect, and when you're working with people you think so highly of and everyone's working so hard, you just feel that you want to pull your own weight. You just want to be as good as everybody else, and that makes me feel I've done a good job. It makes me proud."

She speaks even more proudly about Brad Pitt's performance as a man who reverses in age from his eighties in another Oscar contender, The Curious Case of Benjamin Button. "I have seen it, although not with all the final special effects, but it's great. The effects are amazing, especially with ageing Brad. It's quite remarkable what the director, David Fincher, has done. It really feels like nothing you've ever seen before, and that's so hard to do these days."

Has she been on the set of Quentin Tarantino's movie Inglourious Basterds, which Pitt is now shooting in Germany? "I'd love to go," she says. "We're still trying to figure out the perfect day for me to bring the kids, but there's a little too much blood in a Tarantino film. We're still trying to find a less Tarantino day. What's a good day to bring children on a Tarantino set?"

After Pitt finishes that, Jolie will star in an espionage thriller to be directed by Phillip Noyce. "I'm excited about it because most action films with women are either fantastic or fun," she says, "but this one was actually written for a man and now has been changed for a woman. It was called Edwin Salt and now will be something like Evelyn Salt. It has a lot of action in it. Someone said to me that maybe I chose it because I was breastfeeding a lot when I was reading the script and I was feeling very mommy and maybe I wanted to go out and be tough."

When I ask if she would encourage her own children to go into movies, she hesitates for a moment. "As a parent, you should encourage whatever seems to be naturally coming out of them, whatever it is. Some of them have pretty big personalities, so it wouldn't surprise me. But I'd be nervous, I guess, if one of them wanted to be an actor. I would have to take a deep breath before I could say I was okay with that. But of course I would."

With six children under eight, would she like to have more? "We're having such a good time with our kids," she says. "They're just some of the funniest people we've ever met and we really like hanging out with them. So more just sounds like a great idea. It's hard work, but it's worth it.

"Every child is unique and now to have two at the same time has been a little harder, but it's twice as much fun. There's a lot of love in my home, and I have a great partner. Both of us are there taking care of them, so we each have one in our hands. They're just at that age where they're starting to smile and laugh a lot. The older kids love them. The boys are so good with them and the girls are always dressing them up. It's a really magical time. We're so lucky."

Changeling goes on Irish cinema release from Wednesday next

Thank you Mr Eastwood

"He's extraordinary," Angelina Jolie says when asked about working with her Changelingdirector, Clint Eastwood. "Everyone talks about how quick he is on the set, and that's true. It's because he's extremely decisive and he doesn't mess around. If you ask him a question about a scene, he'll give you a very direct, clear and helpful answer. He's also got a bunch of people around him and they've worked with him for over 20 years. So it's like being in this team with a great leader. He just inspires everyone.

"But he is quick. There was one scene right after lunch one day and I was slowly settling in. He told me I would be lying on a bed and the phone would ring. I lay down on the bed and he started shooting. Then he told me the phone's ringing. I jumped off the bed and ran to the phone in a panic, remembering that my character had to be in a panic. He just said: 'Okay, we're moving on'. That was it. I didn't know what had just happened, but if you watch it on screen, I look very alive - and slightly stunned.

"He works that way because he wants to keep things fresh. Some directors take so long setting up a scene that the actors start thinking a lot. They analyse themselves and they study themselves, and they wonder about the last take they did and should they do the next take differently. With Clint, you have no time for any of that. So it becomes organic. You're too much in the moment to over-think it or to prepare anything. And it does produce some very good work."