In Britain, chestnuts are associated with Christmas. They're as much a part of the festive season as mulled wine, as shown by the fact that 80 per cent of the 200 tons of pre-cooked chestnuts Merchant Gourmet sells in the UK each year is whisked off the shelves in November and December.
But, while chestnuts may make an admirable stuffing for the Christmas turkey or enliven a dish of boiled sprouts, we're only just starting to realise that their uses can extend beyond 25 December. In contrast, the rest of Europe has long valued the versatility of chestnuts, using them in salads or pairing them with chocolate, oranges or cinnamon in puddings. "They're great with all poultry and game," adds Leatham, "or with roast meats, instead of roast potatoes. Probably better for you, too."
Considering that chestnuts have now become so enshrined in our Christmas tradition, it's surprising that few, if in fact any, of those bought in the UK are home-grown. Most come from Europe, especially Portugal and France. Originally from West Asia, the sweet chestnut was first introduced to Europe by the Greeks. In France, entire chestnut woods and forests were planted during the course of the 18th and 19th centuries, when the nuts were eaten fresh, dried over fires or made into flour.
Although chestnut cultivation in France was largely abandoned at the start of the 20th century, the forests remain and the chestnuts are still used extensively in French cuisine, as an accompaniment to savoury dishes or in desserts such as marrons glacés (crystallised chestnuts).
Broadly speaking, there are two varieties - the châtaigne, which has two or three fruits packed together inside its husk, and the marron, which only has a single large fruit. Although the French (somewhat confusingly) often refer to them all as marrons, it's the smaller but sweeter and more flavoursome châtaignes that are commonly used.
Both flourish in the south, especially in thickly wooded areas, such as that around La Corrèze in (omega) the Limousin region. Known as La Châtaigneraie, this is real chestnut country. From about September onwards, it's common here to come across families armed with buckets, gloves and long-handled wooden forks wherever there are chestnut trees. If the trees are on private land, the gatherers may pay the owner for the right to harvest. More often, however, the chestnuts are growing wild. Encased in a fearsome-looking husk, or "bogue", of sharp spines, the ripe fruit simply drops off the tree and lies in the grass until it's picked up.
It's a rare pleasure to come across a tradition that hasn't so much resisted progress as ignored it completely. "It's an entirely natural product," says Leatham, looking around the grove of mature chestnut trees we've come to visit. To demonstrate, he breaks open a chestnut from a newly fallen husk to reveal that a maggot has eaten its way all the way through it. As with any wild food, this is merely an occupational hazard, and a gatherer has to check for signs that the chestnut is diseased or worm-eaten. "There is no fungicide or pesticide used. These are wild plants," Leatham says, cutting off an undamaged section of the nut and chewing it.
His company buys all of its whole chestnuts from the Ponthier family, who are the largest producers of chestnuts not just in the region, but also in the whole of Europe. They, in turn, buy direct from the gatherers at the local markets, where the chestnuts are priced according to size and ripeness. As with so many other things, in the chestnut world, biggest isn't always best. Medium-sized fruit is considered to have the most flavour and so commands the highest prices, while larger chestnuts are usually sold fresh and the smaller ones are bought by producers of jams and purées.
At this point, the rural tradition of chestnut gathering makes way for a more commercial approach. The Ponthiers freeze or vacuum pack around 2,000 tons of chestnuts each year at their factory in Objat, a modern plant that seems incongruously hi-tech considering the chestnuts' rustic origins. After being lightly roasted and steamed to remove the thick brown outer- and furry inner-skins, the chestnuts are hand-sorted to weed out any defective fruit, then either frozen or sealed into vacuum-packs and pasteurised in boiling water - a process which also cooks them.
The process doesn't involve any additives or preservatives. And the idea of preserving chestnuts in itself is hardly new: even the Greeks and Romans used to dry them out so they could be used throughout the year. It's only in the UK that the humble chestnut has been under-appreciated.
But, at last, that seems to be changing. And not before time, believes Leatham. "There is a growing appreciation of their versatility over here," he admits. "If only people realised chestnuts aren't just to have with turkey at Christmas."