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The Egyptians coated them in goose fat and cooked them en papillote. The Romans thought they had mysterious aphrodisiac powers and, in the 19^th century, the French novelist, Alexandre Dumas, of The Three Musketeers fame, wrote, “They can, on certain occasions, make women more tender and men more lovable.”

The food in question? Black truffles, otherwise known to fungi fiends as black diamonds.

The Larousse Gastronomique, the chef’s Bible, defines the truffle thus:

‘A subterranean fungus which lives in symbiosis with certain trees, mainly the oak; it is found in chalky soil or clay, quite near the surface, less than 30cm deep.’

There are 70 varieties of truffles grown globally from California to Australia and 30-odd varieties flourishing in Europe alone. But the king of truffles, and the only variety any serious truffler will get out of bed for, is the Tuber Melanosporum, better known as the truffe noir d’hiver. With its trademark black flesh, striped with thin, white veins, and an aroma somewhere between that of petrol fumes and Gorgonzola cheese, this is the true black diamond.

Truffles tend to be eaten with foie gras, used in recipes with game and meat, or in various sauces and garnishes. The flesh is cut into thin slices, or diced and sprinkled liberally over a dish. The flavour is hard to define, subtle yet unusual, while the true truffle cognoscenti profess to enjoy them best when cooked with some butter and served like a canapé, or braised with some white wine in a pastry parcel.

The best place to go in search of the black diamond is the Lot region of southwest France, a gloriously scenic backwater with easy access from the flight hub of Toulouse.

And that’s exactly why, on a nippy afternoon in early January, the height of the truffle-hunting season, I find myself in a wood in rural France with Marthe Delon, a local farmer, a group of Japanese truffle traders and Kiki, one of the last working truffle pigs in the Lot.

A pig in muck

Four-month-old Kiki is clearly relishing the spotlight and puts on a fine show of sniffing out potential truffles then digging up the earth with his snout. Discipline is essential for a well-trained truffling pig, however, and Marthe is a strict taskmaster, policing her porcine helper with a stiff wooden cane and a stout rope lead.

A stocky women in a floppy Credit Agricole hat and a smile that attests to a lifetime of poor dental hygiene, the Japanese traders clearly love the theatre of the hunt as Marthe, the digger in truffle parlance, pursues Kiki through the woods behind her farm like a peasant farmer dominatrix in a grubby apron.

“Non,” she exclaims, administering a hefty thwack to Kiki’s hind legs. “Allez, cherche,” she demands, forcing Kiki to let out a disgruntled shriek and reluctantly relinquish a tasty morsel of shrub.

The Japanese, meanwhile, snap photos and applaud enthusiastically. Only when Kiki stops truffling to urinate voluminously close to a Tokyo-purchased brogue do the smiles give way to a moment of awkward silence.

Truffles form from spores during June and develop during the summer months, reaching maturity just after Christmas due to the favourable combination of local soils and climate. From January to March, the main truffle season, Marthe and Kiki are out truffling most weekends and on Mondays, taking advantage of the afternoon sun and softer earth to hunt truffles for the Tuesday market at the nearby village of Lalbenque.

Dogs are increasingly used these days to sniff out the powerful aroma of the buried truffles but Marthe insists that a well-trained pig is far superior. Dogs, she explains, tend to mistakenly dig up truffles that are not yet mature and, once they come into contact with the oxygen in the air, the truffle is ruined, rendered worthless. Bought for €100 from the market, however, Kiki has developed a nose finer than that of a Bordeaux wine merchant and, in a two-hour afternoon truffling session, can unearth up to 850g of top-quality truffles.

If he slacks off, Marthe simply helps to focus his mind by administering a hearty thwack of the cane to his perky pink posterior.

Foodie festival

The next day we head to the tiny village of Lalbenque, the truffle capital of France, located 17km southeast of Cahors. It’s two in the afternoon and the tiny main street is a sea of berets and cheroots. French farmer peasant chic is definitely le look du jour.

Lalbenque plays host to the world’s largest truffle festival at the end of January each year and, each Tuesday during the truffle season, is the location of a boisterous truffle market. In the immediate run-up to the opening bell, there’s a tangible frisson of truffle-induced tension in the air. When the chimes ring out and the red standard is raised to let trading begin, a frenzy of activity follows with deal struck, scales loaded and old scores re-opened.

It’s been that way for over 80 years and the truffle purists wouldn’t have it any other way.

The latest challenge to the status quo, however, comes from an altogether unlikely source: the world’s fastest-growing economy. About ten years ago, farmers in the north of Yunan and south of Sichuan provinces in China discovered that foreign clients would pay big bucks for locally grown truffles.

These Chinese truffles, the Tuber Indicum, are of inferior quality with less aroma and taste than the truffles of the Lot, but cheap imports soon started flooding the market with unscrupulous dealers passing them off as bone-fide black diamonds.

Today over 10 tons of Chinese truffles enter the European market each year, although local truffle syndicates controlling the quality ensure that few end up for sale at Lalbenque’s market, the majority sold direct to hotel kitchens. The National Institute of Agricultural Research (INRA) now carries out random DNA testing to flush out bogus dealers with anyone caught deceiving the consumer heavily fined.

The prices at the Lalbenque market do, however, fluctuate from 700 euros per kg for a sale to a small trader to 400 euros per kg for leftover truffles to use in sauces and preserves. For the insider knowledge on insider dealing, therefore, we pay a visit to the Cahors-based office of Pebeyre Truffles, a family business that has traded high-quality truffles for four generations.

There, hunched over a tray of truffles in a blue overall, we find Pierre-Jean Pebeyre, the head of the business and a man whose client list is more closely guarded than Elton John’s wedding invitation list. Japan, Hong Kong and Australia are his major markets, London’s Ritz Hotel a regular customer and what he calls “individuals of private means” often call his mobile phone, talking prices in hushed, conspirational tones.

Even today Pierre-Jean and his father personally inspect every truffle leaving the warehouse after cleaning and sorting.

“What I look for in a good truffle is the combination of firmness and subtlety,” he says, sifting through a tray of freshly washed truffles with the keen eye of a diamond trader.

“The clue to the quality comes when I cut a piece of skin to see the contrast between the black flesh and the white veins. Top quality truffles fetch around 600 euros per kg at current market rates.”

For the Pebeyres, however, the future looks uncertain. When the business started in 1897 there were 800 tons of truffles produced in France with 25 tons in the Lot. Today there are less than 20 tones in all of France. “I think in ten years my métier will be dead,” he predicts gloomily. “The ecology of rural communities has changed, leaving trufflers marginalised. The only way for this business to survive is to diversify into other high-quality products, such as foie gras while maintaining a small truffle tradition.”

Yet while the volume of truffles may be declining, interest in the folklore surrounding them is not. Science remains unable to cultivate truffles under laboratory conditions while even truffle purists can’t find the words to describe the idiosyncratic flavour.

“For me, it’s a very strong, powerful flavour, but also very fragile – if you cook it too long, it is destroyed,” says Gilles Marre, head chef at Cahors-based restaurant Le Balandre and a member of the Bonnes Tables du Lot, an association of local chefs. “Maybe that’s the key to its enduring mystery,” he adds, “It’s a balancing act.”

The ultimate quest

Back in the woods, Kiki is busy truffling away, blissfully unaware of the socio-economic effects of rural migration that plague the contemporary truffle terroir. He sniffs the ground, locates his target and starts burrowing frenziedly with his snout. When he unearths a plump, earth-covered truffle, Marthe proffers a handful of dog biscuits, the Pavlovian reward that ensures Kiki doesn’t scoff the merchandise.

Our quest for the black diamond is complete.

After the Japanese visitors disperse and Kiki is returned to his enclosure, he looks as happy as a pig in the proverbial. But life is cruel for trufflers: despite his sterling efforts today, this little piggy’s days are numbered. “The life of a truffling pig is happy but short,” Marthe grins a wide, toothless grin.

“Come November we’ll be training up a new pig for next season,” she adds.

“And Kiki will be keeping us in pate and sausages throughout the winter.”

* This story won the French Travel Article of the Year, awarded by the Association of British Travel Organisers to France (ABTOF), in 2006.

It was originally published in bmi Voyager magazine.