Two years ago, in the middle of the campaign for her universally acclaimed, platinum selling debut Frank, Amy Winehouse began thinking about what she'd like to do with her second record. Frank was her grand and suitably blunt-speaking break-up record, sometimes a little bitter, with a maturity in the vocal delivery that was never less than sweet. It won her a battalion of fans around the world and marked her out as one of the most distinct new voices in pop; confessional, elemental and with that rarest of combinations: humour and soul. Amy had cut through to the core of the human condition with her debut, adding her own jazzy witticisms to the legacy of the greats. So how to follow it up?

Musically, she was sure where she wanted to go. "I didn't want to play the jazz thing up too much again," she says now, sitting in the snug of her favorite Camden boozer. "I was bored of complicated chord structures and needed something more direct. I'd been listening to a lot of girl-groups from the fifties and sixties. I liked the simplicity of that stuff. It just gets to the point. So I started thinking about writing songs in that way." You can hear it on the subtle Supremes-referencing intro of "Back To Black." But her reach stretches further. While the girl-groups of the sixties to which she had become enthralled contained their vocals, Amy can break loose with Aretha-style vocal stylings on "Just Friends" or by turning the whole idea of drying out into a gospel spiritual on the stunning opener "Rehab." Which other female British singer could turn the opening line on her album - "try to make me go to rehab/I say no, no, no" into a churchy stomp.

Armed, as ever with only her acoustic guitar, a packet of ever-present fags and a bursting imagination, Amy set about distilling her experiences since the arrival of Frank into song. She is one of the most delightful storytellers on the subject of her own inspiration. "If I haven’t done it, I just can’t put it into a song. It has to be autobiographical." Songwriting for Amy is like keeping a journal. "It’s an exorcism. I get all my stuff out there. If I didn’t have this medium to get my experiences across, I would be lost." 'Lost' in Amy's language concurs with the 'lost' of the soul greats: just listen to her heartbreaking metaphors in the sublime "Love is a Losing Game." This is classic modern songwriting and delivery; brief, to the point and drenched in emotion.

The experiences themselves. Where to start? The Nas gig that she didn’t get to go to because some guy wouldn't get her a ticket? How do you manage to turn that into a tale of female empowerment, as she does on the superb "Me and Mr Jones." The eternal love triangle of one ex-boyfriend who she knew was no use and a new one who has his name emblazoned right next to her heart in a tattoo? The pain of heartbreak? The joy of new love? The stunning personal epiphany that perhaps you can behave just as badly as all those guys that have messed you around and stamped all over you, as she declares unapologetically on "You Know I’m No Good?" Or the feeling that when things go wrong you deteriorate into a black space that you have to physically lift yourself out of? That's there on the bluesy smooch of the title track, "Back To Black." While she is interested in deep emotional resonance of love both lost and found, she is just as happy decrying the boy who comes round to her house and smokes all her pot "Addicted." Amy is one funny, smart lady. And does it need pointing out that there's hardly enough of those to go round in the current pop milieu.

Amy's refined new songwriting approach has been grafted onto some of the most astonishing, stunning material of her short career so far. Her fearlessness as a lyric writer has no peer. While other girls of her young vintage - she's still only 23 - like to turn a comic motif out of their relationship histories or deal in generic pop emotions, she smarts at the idea of being anything less than brutally honest. "What's the point of not being?" she quizzes, with a sanguine charm. Yet she knows she can be funny too. "You've got to get that in there. Life is funny and sad, sometimes both at the same time."

Amy reunited with Frank producer Salaam Remi in Miami for a two week, whistle-stop recording tour and they found magic once again. Promptly she decamped to New York to work with man of the moment Mark Ronson, managing to book a spare moment between his work on the Lily Allen, Robbie Williams and Christina Aguilera albums. In her three weeks of studio time she found a new soul and direction, one that both channeled the girl groups of her fancy but placed them slap bang into the middle of modernity. "I'm not quite sure how the record turned out to sound so complete but I knew that when I decided to record it in a couple of weeks I wanted it to sound like it had been." The songs are built around the classic three minute pop motif. Nothing is over-egged. Back To Black is a coherent piece, built for listening in one sitting.

Amy isn't certain how she turned into one of those girls that aren't afraid of the darker experiences in life and turning them into something witty and truthful, but she's glad it turned out that way. "I always want to feel something. Because I know that I can write a song and deliver it to get it out of me if a situation turns bad. I understand myself so much better after I've written a song about something."

Music is not just her defense mechanism. It is her lifeline. In the two years since Frank cause such a ruckus by presenting this voluble and extraordinary human being centre stage, Amy thinks its only circumstances that have changed, not her. But you can see it in her increasingly creative body art, her slightly more aggressive eye make-up and the great swoop of black hair that cascades across her face and down her back. This time, Amy Winehouse has charted her progress from girlhood to womanhood. It suits her. You'll be pleased to know that she met a guy a few months ago - they share the same birthday, so it's fate, see? He loves her and she loves him. She is untangling her mess, finding her true spirit and learning to break loose from the demons that have followed her. She's doing it all with a smile on her face. Back To Black, with its stunning array of loosely strung, funk-inflected joints sees her finally getting to a good place with herself.