As a chocolate shop proprietor, I am used to being sent free samples, but when I broke off a piece of a bar from Grenada in the Caribbean, I was stopped in my tracks by just how good it was.

I looked up the Grenada Chocolate Company's website and found what claims to be the smallest chocolate factory in the world, working from "tree to bar". Most chocolate factories are rigorously climate controlled to ensure cool, dry conditions - heat and humidity being the worst enemies of chocolate. So who would attempt to do such a thing on such a small scale?

The answer was Mott Green, who arrived on the island in 1987 looking to chill out on the side of a mountain. After building his bamboo hut and solar hot-water system, he discovered cocoa "tea", Grenada style, thanks to a neighbouring farmer. Soon Mott was puzzling how he could use the local beans to make chocolate bars, and after years of inventing small-scale versions of industrial equipment, the Grenada Chocolate Company was born in 1999.

I called Mott to place an order, but also to arrange a visit. The drive across the island was stunning: away from the white sand beaches and up through the Grand Etang national park to Hermitage St Patrick's in the mountains. Grenada is a tiny island, 18 miles by 24, and this was about as far from anywhere as you can get. But get into any taxi in St Georges, and they will take you there in just over an hour - you can do the tour and buy the chocolate.

To call it a factory is stretching things. It is a domestic house, used purely for chocolate making. Behind is a plot of land where cocoa grows. All of this in 30C-plus temperatures and high humidity: breaking all the rules. And yet here was some of the best chocolate I have ever tasted: organic, ethical and made with solar-power right where the cocoa grows. The whole operation defied belief.

A co-operative system ensures that all the workers, from the farmer to the chocolate maker, are paid the same rate. Not surprisingly, it is some of the most expensive chocolate in the world, at around £45 a kilo. Now it's also some of the rarest.

On September 7 2004, Hurricane Ivan ripped through the island; 90% of the buildings were damaged, the electricity was cut off and travelling around became almost impossible as trees blocked all the major roads.

In Hermitage St Patrick's, the factory was largely undamaged, and the Grenada Chocolate Company became the focal point of the community. It still had its solar electricity supply and lots of chocolate (a delicious high-energy supplement), which it gave free to all comers. At night, DJ Sly set up a huge sound system - loud solar-powered music lifted the spirits of the villagers who were confined to their candle-lit homes - a formidable demonstration of the power of renewable energy.

Then, 10 months later in July 2005, Hurricane Emily flattened most of the trees that had survived the first time around. Times have been difficult at the factory, with very few cocoa beans now, and a work force to pay. But Mott's vision is undimmed: more cocoa is being planted and windbreaks put in place to minimise future storm damage. My shops, Rococo, are involved in this regeneration, and the future for cocoa, chocolate and sustainable farming on the island is bright.

· Grenada Chocolate Company (grenadachocolate.com) 113g bars £5.50 each from Rococo Chocolates (rococochocolates.com) 321 Kings Rd, London SW3 or 45 Marylebone High St W1.