Damian Allsop meets me at the door of his workshop round the back of a small industrial park in a chocolate-box pretty Buckinghamshire town. The autumn sun is shining. People are standing about, shirtsleeves rolled up. There's Rick from the taxi company and a pretty young woman smoking a fag. Round the back there's an unprepossessing set of green double doors. There's a chain next to it. I pull it and suddenly the doors open, releasing an overwhelming smell. It's like a mix of sugar and milk all in one nostrilful of air.

In an instant it takes me back to when I was a kid and my parents would take me to the swimming baths in Slough. The minute you hit the first of the endless traffic lights, you could smell it. The Mars factory. The air would become so sickly sweet, it made me queasy. But this is different. The smell that emanates from Damian Allsop's workshop is so rich, so dark, it makes me salivate. So I walk in through the door and find myself in a small room. It's not quite Willy Wonka's factory. There are no Oompa-Loompas. There's just Allsop and his Catalan girlfriend Anna and endless piles of chocolate - stacked up, heaped up, in bundles on a table and trundling out of a machine in the corner. Anna, who is dressed in white overalls and protective hat, is blowdrying some chocolate rectangles as they appear from the machine.

In the middle of it all is Damian Allsop. Although he is 38 years old, he looks like a schoolboy. He has glasses and gingery hair all smoothed down. He pumps my hand enthusiastically as he walks me further into the room. 'Can you smell the chocolate?' he asks me. I tell him I can. 'Strange,' he says. 'Everyone who comes in here says it smells of chocolate but Anna and I can't smell it at all.'

This, of course, is not strange at all, because Allsop has been working with chocolate for years. Chocolate is his life. 'Isn't it everyone's life?' he says, looking puzzled. To Allsop, chocolate tells the history of the modern world. 'You can follow how societies were formed by following the movement of chocolate round the world. The Aztecs perfected the art of making chocolate but then they died out and the Spanish took over and changed the way chocolate was made.' Allsop could go on forever. 'It's fascinating, you see,' he says. 'Everyone loves chocolate. There's something wrong with you if you don't like chocolate. You have to be lacking in something not to want to eat chocolate every day.'

But more than that, Allsop is causing a mini-revolution in the world of chocolate-making. For he has, he thinks, found the key to making the perfect chocolate. 'It's what we all want,' he says. 'It's what chocolatiers dream of - to find their voice, the meaning of life through the creation of the one perfect chocolate. I have spent the past few years of my life ripping up my recipe book to find it. It has been like going on a hellish but wonderful journey.'

Over the past two years Allsop has made a growing name for himself because of his obsession with junking the usual rich butter and cream-based ganache that usually fills chocolates and, instead, perfecting his own closely guarded formula.

'I use water!' he says, pointing at a small food mixer. 'I mix it all in there. It's incredible. Just think about it!' He is striding up and down his small workshop now. 'I have thrown away hundreds of kilograms of chocolate because I thought I couldn't get the right flavour when it came to doing a water-based ganache. I mean, it made perfect sense to use water. Chocolate is egotistical. It doesn't like anything else to mess with it. Water is the least-flavoured liquid, but how to do it? How to do it? I had to find the science to create what I wanted and it was very difficult.'

He hands me a chocolate from the bundle sitting on the table in front of me.

'What do you think of this?' he says. He stares at me intently as I put the chocolate in my mouth.

I take a small bite. At first I am not sure what to think. It doesn't taste like chocolate. It tastes like, well, nothing I've ever tasted before. At first a burst of passion fruit passes across my tongue.

'Passion fruit!' Allsop says excitedly. 'Can you taste it?' But just as I've picked up on the flavour, suddenly it's as if I've taken a gulp of coffee.

'It's coffee!' I say in amazement. 'It's not passion fruit any more. It's coffee!' Then I taste chocolate and, finally, something more buttery. I am absolutely flabbergasted.

'That's incredible,' I say. Damian Allsop smiles.

'Yes, I got it right. And, what's even more exciting is that these chocolates are good for you. There's no lactose so people with allergies can eat it and, without the butter and cream, there are fewer calories.'

'That's perfect,' I say.

'But it's not perfect,' he says. 'Nearly but not yet.'

There is no doubt that Damian Allsop is an obsessive man. He is self-taught. Neither of his parents were in the catering trade - his father is now a psychotherapist who lives in London, his mother stayed at home and looked after the children. He was born in Grimsby - not that he has an accent because he had a peripatetic early life moving from one place to the next. 'My dad worked for IBM and his job moved around a lot but I liked it,' he says. He lived in Southampton, Wales and then, when he was 13, London. 'My dad became a therapist. I remember sitting in his room. There were all these cushions and I'd watch people bash them to get their anger out. I've used that technique when I've been stressed out about my recipes not working.'

He left school at 16 and started cooking. 'That was an odd thing to do in my family. My mother didn't cook but I became passionate about it.' He decided that desserts were his thing so he went and trained at the Hyatt Carlton making endless millefeuille and chocolate and sugar sculptures.

'I learnt the classics,' he says. 'But I was frustrated. No one questioned why we made a gâteau in a certain way. But I wanted to know why things happened. Why did the flour thicken? For me, making pastry is a science. You are making textures with that pastry. I kept asking myself, what changes that texture? I like the search for answers.'

His search for answers took him to the kitchen of Joël Robuchon in France. 'I was there at the same time as Gordon [Ramsay],' he says. 'God, we worked hard. Joël was the chef of the centre and it was all very focused. Gordon was amazing. He stuck it out but it wasn't for me.' Allsop says it was too traditional for him. 'It was recognised as being the best kitchen in the world. It had three Michelin stars but I wanted to do cutting-edge desserts. You know, the world of the dessert trolley and sculptures made from pastry were not for me.' He also says that he tired of all the hierarchy. 'At the end of a shift you had to stand and be inspected by the head chef. You know, you'd worked so hard but then something might be slightly out of place so a pail of water would be turned up over the kitchen floor and you'd have to start cleaning all over again.'

So he left - a move he sometimes regrets. 'I was young. Maybe I didn't realise what an opportunity it was.' He came back to England and ended up working alongside Angela Hartnett, Marcus Wareing, Mark Askew and Ramsay in Ramsay's first restaurant, Aubergine. He stuck it for two years and then left. 'It was nothing to do with Gordon, who was amazing. It was incredible to watch him, exciting really. He has such drive and passion. We would just watch him in awe. I just wanted to learn more.' He realised he didn't feel settled in London. 'I had loved France as a place to live,' he says. 'I got itchy feet. I wanted to go abroad again.'

This time he went to Catalonia. 'I was so excited by how the Spanish felt about their food. They take time out to eat. It is very ritualistic. I fell in love with the place.' It was here that he met Anna. 'I'd marvel at her. She'd eat weird things like toasted bread with salt and chocolate. It's traditional in Catalonia but it got my mind whirring.'

He happened to be there at the same time as Ferran Adrià was becoming talked about for his experimental food at elBulli - now considered to be the best restaurant in the world. 'I got a job at the two-star restaurant El Celler de Can Roca with Joan Roca. The two restaurants - mine and elBulli - were close really. We shared things and, gradually, I became very excited with the science of what was happening around me. Ferran showed people like me that there were other ways of doing things.'

It was about this time that Allsop started thinking about chocolate. 'I got this idea of the water. The science was there, but could I do it? Could I take everything I had learnt and rewrite it all?' The answer came when, after forgetting his keys, he tried to climb up the side of a two-storey building and fell from a drainpipe. 'I broke my feet,' he says. 'I ruptured my back.' He ended up spending six months in a wheelchair. 'What else could I do but think?' he says. 'It was good for me. I had been working so intensely, I had to stop.'

In 2002 he met legendary Tuscan chocolatiers Alessio and Cecilia Tessieri of Amadei, and tasted their Chuao chocolate. 'Chuao showed me how to love chocolate. It's satisfying to work with and I think of chocolate as being like wine.' He tells me there are varietals of chocolate almost in the same way there are varietals of wine. 'It depends where it's grown and the taste of the seeds as each seed in a pod is slightly different. Chocolate has many different qualities. It evolves like wine. When it comes to the end product, I choose chocolate for its balance and length of flavour.'

The other thing Allsop came to realise, while in his wheelchair, was that, if he was going to work 12 hours a day, seven days a week, he wanted to do it for himself. 'That's why we came back,' he says. 'To look for a factory and start this dream I had.' He hopes he and Anna will be able to hire more people soon. 'It's a strain,' he says. Anna nods fervently. 'We have no financial support.' Anna nods even more fervently. 'I found this place for a good price and I bought the tempering machines - it's all about the temperature of the chocolate really - but I had no idea if it would work.' For weeks, it didn't. 'Anna couldn't believe it. I had spent eight years rewriting all my recipes. One day she screamed at me, "This has to work! You told me it would." And then, people came to taste the chocolate and they liked it.'

Now he has clients everywhere. They sell to delis such as Zafferanos and the Fat Delicatessen in Balham. 'Angela [Hartnett] is going have them at York & Albany. She's been really supportive. She let us practise making chocolates when she was at the Connaught and she has three of mine at Murano - a cherry, an amaretto and a hazelnut crunch.'

The chocolates come in nifty boxes, designed by Allsop of course. They are orange and grey and the logo is CH2OCOLATE. His main business, however, comes from restaurants. 'I do bespoke chocolates for them,' he says. He has local support from Michelin-starred chef Tom Kerridge at the Hand and Flowers and Adam Simmonds at Danesfield House, both acclaimed restaurants in Marlow. He also supplies chocolates to Foliage, Hibiscus, Hotel Tresanton, Restaurant Sat Bains and the Felin Fach Griffin Inn near Brecon.

Before I leave, I try more chocolates - pear and anise, olive oil, olive oil with aged balsamic dripped on to it, lemon verbena, an acid yoghurt with a pistachio inside, salty liquorice, one tasting of the local Rebellion Beer and the purest mint I have ever tasted, as if someone had plucked it from my garden. They are all exquisite. Finally Damian Allsop hands me a chocolate full of cherry jelly and dusted with raspberry powder. 'These I have made for Coutts bank,' he says. 'Delicious aren't they?'

I ask him why his chocolates taste so fantastic.

'Because I understand how your tongue receives flavours. I choose where to put a certain flavour so that you can have a conversation in your head about that chocolate.'

'But how do you make them? I ask him, slightly desperately.

He touches his finger to his nose.

'I will never tell,' he says smiling. 'Never.'

• damianallsop.com. Damian Allsop's special Christmas range is available at Fortnum & Mason, fortnumandmason.com

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