What's hot and what's not: The layers of flavour in a chilli are akin to the complex taste of wine, says Joanna Blythman

The Cool Chile Company operates from a pleasant west London flat, whose interior is like a fantasy Indian pueblo. Wooden shelves are stacked with various chilli peppers - dried, pickled, salsas - wedged among jars of blue corn meal, Mexican chocolate, corn husks, annatto seeds and masa harina tortilla flour.

All the kit for Mexican cooking is here. There is an open fire in the living room, over which Dodie Miller, who runs the company with her partner, David Bashford, has just smoked some rabbit after tenderising it in a chilli marinade.

'I have to admit I'm getting obsessed with chillies,' she says. And the Cool Chile Company, set up last summer, reflects her obsession, offering a range of Mexican chillies (organised by heat, flavour and suggested use) to British cooks.

I spent an afternoon tasting my way through the chilli selection, and that was enough to appreciate how the subject can grip you. Since then I have been eating them at every opportunity. Robert Mondavi, the American winemaker, likens the layers of flavour in chillies to those in complex wine, and he has a point.

We started at the mild end, nibbling some roasted, peeled and dried Pasado chillies, which tasted like caramelised apple, with a hint of lemon and celery. Ms Miller awards this a heat rating of between three and five out of 10. For me this was extremely mild.

The long, tapering burgundy-red Guajillo was also mild, reminiscent of citrus fruit and Agen prunes with a smell of pine and just a lingering heat in the throat (heat rating 2-4). These were not dissimilar to the Anchos or dried Poblanos, also sweet with a slight sun-dried-tomato flavour. Then came the raisiny, leathery flavours of the tiny, rattle-shaped Cascabel, still mild at heat rating 4. four.

All of these taste predominantly fruity; but the flavours change with the Mulato (heat rating: 2-4), where a superficial resemblance to dried cherries gives way to liquorice and peat smoke. There is even more liquorice in the Pasilla or 'little raisin' (heat rating: 3-5).

Real heat, at 6-7, arrives with the Chipotle - a dried, smoked Jalapeno said to be a favourite of the Aztecs, with an extraordinary flavour that comes from smoking over pecan, hickory or oak. When the heat dies away, the flavour lingers. Lovers of lava-hot vindaloo will find what they crave in the Habanero (heat rating: 10), which breathes Marmite aromas and tropical fruit tastes, as well as fire.

Along with these dried varieties, Ms Miller also stocks various dried pepper flakes, powders and a range of fresh chillies such as the pale yellow-green, mild Caribe - marvellous in omelettes.

All these she supplies to shops and restaurants. But even this breathtaking array of flavours and heats is just a fraction of the possibilities. Mexico State University recognises at least 1,000 strains; the chilli is known as the 'slut of the plant kingdom', because it breeds so easily.

Although she lives in London, Ms Miller is American; and she says that in the US 'there is a chilli pepper magazine, a Hot and Spicy Food Festival, and whole product ranges centred on chillies'. It was on a trip to America, to the South-west, that she became keenly interested in chillies. Back in London, and excited by the idea of opening a Mexican restaurant, she found that chilli varieties which were common in American-Hispanic food stores were not available in the UK.

With the help of the chef-restaurateur and chilli guru Mark Miller (no re1ation), who runs the famous Coyote Cafes in Santa Fe and Washington, she tracked down a supply of dried chillies to import into Britain. The restaurant idea gave way to a chilli stall; now she can do mail-order in dried chillies and wholesale in fresh, and is going from strength to strength.

Ms Miller's business looks likely to thrive further because chillies are addictive, like chocolate. 'Chillies are exciting, because they mimic a rush of adrenalin. They make your heart pump faster, you breathe faster, your sweat glands get going and you get a warm feeling in your stomach. All this gives you a sort of serene feeling, like someone who has just climbed a mountain but without the effort,' she says.

Science supports this: chillies all contain capsaicin, a substance concentrated in the seeds and membranes which are thought to produce endorphins in the body to block out pain. In the US, creams based on capsaicin are used to treat painful conditions such as shingles.

Chillies are also thought to have other beneficial properties - stimulating salivation and digestion, reducing the body's absorption of fat.

Had she encountered any resistance to chilli? 'There is still a lot of educating to do. Some people worry that it will ruin their palate or numb their mouth. Actually, chilli has the effect of opening up your taste-buds and awakening the pores on your tongue. Dried chillies, especially, are like a spice - they enhance other flavours.

'You do have to build up to chillies. They are an acquired taste: you eat a little bit, then a little more, and you get to the hotter ones gradually.' Ms Miller does not talk casually about heat. 'The degree of heat in a chilli depends on the amount of capsaicin, measured in something called Scoville units, ranging from 0 for ordinary red or green peppers to 300,000 for the hottest chilli. Texan researchers have shown, for example, that the Habanero is a thousand times hotter than the medium-hot Jalapeno.'

The bad news for those of us who buy chillies from sources less well informed than Ms Miller is that colour is no guide to heat, and nor is size or shape. Two chillies from the same plant can vary widely in strength - a fact you may discover to your cost as thousands of Scoville units hit your mouth.

To make matters more complicated, different chillies apply their heat in different places. Unlike horseradish or Japanese wasabi (which anaesthetise the sinuses), chillies go for the throat or the tongue, depending on the variety.

In terms of first aid for chilli eaters, a friend found out the hard way that you should never rub your eyes after touching chilli: he rolled around the floor while his distressed partner poured cold water in his eyes. For a too-hot mouth, a piece of cheese is a more effective cure than water or beer.

Given the sheer scale of the subject, and the fine nuances of flavour and heat, even confident cooks might find chilli a bit daunting. So, although Ms Miller sends out recipes with each chilli variety, she urges that cooks should feel free to incorporate one variety at a time in dishes they already make.

'I'm not advocating Mexican food: it can be too heavy. But chillies blend well with Mediterranean ingredients. Guajillo, for example, makes a great pesto when mixed with pumpkin seed, roasted garlic and olive oil. A British dish such as sausage and mash is great with chilli gravy; a chilli can transform tomato soup or sauce.'

But her founding principle is knowing what you are dealing with. 'In the US, chillies were just chillies at first; then named varieties such as Scotch Bonnet crept in. Named varieties are still rare in Britain and I am trying to correct that. Another good sign is that Sainsbury is doing three different fresh chillies with a flavour and heat guide on the pack.'

Britain is warming to the chilli.

The Cool Chile Company, Unit 7, 34 Bassett Road, London W10 6JL (081-968 8898). (Photograph omitted)