Sharon Shannon Big Band, The Picture House

Like back home in Dublin, catching up on some shut-eye, or chilling on the sofa to the songs of Jacques Brel, the great Belgian songwriter whom she made her name interpreting.

"I think I'm losing the plot," announces the raven-haired beauty in her soft Irish brogue. "I just added a button to the DVD that allows you to meow like a cat if you press it. I must be going mad."

O'Sullivan has good reason to be tired having just returned from Australia and New Zealand – "Great fun, but exhausting." So it's perfectly understandable that the jet-lagged singer would like nothing more than a few days to kick back and recharge the batteries. Chance would be a fine thing.

As soon as she's done with the DVD, she's off to play four nights straight with the Sharon Shannon Big Band on a mini-tour that stops off at The Picture House tonight.

Following that, O'Sullivan hits the road again on a tour that sees her through to mid-July. Then, after only a fortnight's recuperation, the Fringe's favourite cabaret singer will be back here in August, performing in the city where she made her name.

"It's a long few weeks ahead," she sighs. "I woke up this morning and it hit me. I was like, 'Oh. My. God'.

A mention of the word Edinburgh and the jaded star suddenly perks up. "Oh, it's a city I love so much," she purrs. "No matter how tired I'm feeling now, I know that as soon as I set foot in the city I'll be ready to get up to all sorts of mischief."

Much of that mischief could be had with Irish wildman Shane MacGowan, the Pogues frontman who is supporting Shannon alongside O'Sullivan tonight.

"That's going to be fun, because you never quite know what you're going to get with Shane," she explains. "You always have to expect the unexpected."

Being very much Shannon's own show, O'Sullivan will only be performing a few numbers tonight, one of which will be a duet of Fairy Tale of New York with MacGowan (O'Sullivan singing the late Kirsty MacColl's lines).

"That might be a little strange doing that song when it's not Christmas," she laughs. "But it's a thrill to be performing with Shane, who is someone I have so much respect for."

It won't be the first time she has shared a stage with Ireland's self-styled gutter poet.

Indeed, it was MacGowan who handed O'Sullivan her big break a few years ago when he called her up out of the blue asking her if she could get herself down to Dublin's Olympia Theatre in 20 minutes flat to duet with him.

"Yes, and we've crossed paths a few times since," she laughs, taking up the story. "I was in A&E a couple of years ago, and I got a call asking if I'd like to sing with him that night on the Late Show. I wasn't really fit to do it, but I thought 'What the hell?', and told the nurse that I'd be back in the morning.

"I had this massive abscess, so I didn't look so great," she adds, laughing. "I remember I put on these tight little shorts, thinking that would keep the attention off my face. I'm not sure that worked."

Raised in a small village by the sea in County Cork, Ireland (her English father, a Formula 2 racing driver, met her French mother in Monte Carlo), O'Sullivan fell in love with Brel's vivid portraits of love, sex, drunkenness and death as a child.

She recalls, "My parents had an eclectic mix of music at home – the Beatles, the Stones, Serge Gainsbourg, Brel and classical. We were left to our own devices with the records, so a love of music was always there."

Before she became a singer she trained as an architect and while studying, travelled to Germany, where she first experienced cabaret.

Enchanted by the dangerous excitement she witnessed in the clubs of Berlin, she decided to combine her fascination with Brel with her desire to perform.

"In Berlin I discovered a very direct way of singing and performing I hadn't known before," she says. "I never realised that you could sing and act at the same time. It was a really intimate way of singing, not a beautiful way of singing and it was amazing."

It's an art she has long since perfected. The singer's sultry stage presence has beguiled audiences and critics alike since she first appeared at the Fringe in 2004 - though it almost didn't happen after the eleventh-hour collapse of the venue she was booked to play.

"For years I'd really wanted to perform at the Fringe," she recalls, "and it looked like that dream was going to come true when I was invited by a new venue called the Wigwam Tent." But the dream almost turned into a nightmare.

"The venue collapsed financially two weeks prior to the Festival opening," she says. "Luckily, within a few hours, The Spiegeltent offered me some dates and also a slot in their late night burlesque cabaret, La Clique.

"Too late to appear in the Fringe programme, I had one week to decide whether to go and risk financial ruin performing two different shows – Camille Sings Brel and The Dark Angel – or just not go at all. Me being the way I am, I opted for financial ruin," she adds, laughing.

It was a risk that paid off. O'Sullivan earned five-star reviews for her own show, while La Clique became the sell-out hit of the year with the likes of Christian Slater, Paul Merton and Will Young queuing up for tickets.

Sharon Shannon Big Band featuring Shane MacGowan and Camille O'Sullivan, The Picture House, Lothian Road, tonight, 7pm, 18.50, 0131-221 2280