Pale and stodgy imitations have tarnished the image of the Cornish pasty. Alice-Azania Jarvis learns how the real thing is made

Stilton. Gorgonzola. Champagne. Together, the buffet at a posh Christmas party. Individually, holders of the much-sought-after Protected Geographical Indication awarded by the European Union. Next to add its name to the list will be the Cornish Pasty – at least that's what Wayne Day is hoping. Managing Director of Tamar Foods in Callington, and a founding member of the Cornish Pasty Association, he has been front-and-centre of the region's long-winded battle to achieve culinary recognition. "We don't want what happened to cheddar to happen to us," he explains.

Quite right, too. What happened to cheddar, and what happens to countless other regional specialities, is that they became too popular for their own good. Ever-cheaper versions are made, each one fractionally less authentic than the one before. In what the Cornish Pasty Association refers to as the "sausage slicer effect", the end product is gradually debased and with it the reputation of the original. Thus, to millions of people around the world, cheddar is not the slightly sour, crumbly cheese of West Country acclaim but a vaguely futuristic piece of pre-sliced rubber. The PGI is designed to prevent that, forbidding food sellers from labelling goods under specific names unless they meet a set of established criteria. Stilton, for instance, must be made in either Derbyshire, Leicestershire or Nottinghamshire and must use pasteurised milk.

Day and co first lodged their claim for PGI more than eight years ago – these things don't come easily – and are expecting a decision some time in the new year. In the meantime, the campaign has collected the support of Hilary Benn, the local MP Colin Breed and MEP Graham Watson. Of course pasties, in the loosest sense of the term, are everywhere. I pass two stands selling them on the way into work. They are a frequent, not unpopular option for lunch. The other day I saw Hugh Fearnley-Whittingstall make one on television. Indeed, according to the Pies and Pasties 2010 report from Mintel, sales climbed by 5.2 per cent between 2007 and 2009.

Cornish pasties, though – the proper, soon-to-be-protected ones – are rather more difficult to find. My first taste of one was just two years ago. I was on holiday in Penzance and, amidst the disappointing drizzle of a summer holiday spent in England, had sought comfort in its gentle, peppery warmth. A far cry from the flaky convenience store variety, it was grade-A stodge: buttery, salty-sweet, leaving a sturdy weight inside my stomach. In other words, it was perfect. The thing is, in order to be a proper Cornish pasty, the list of criteria to be fulfilled is really quite daunting. For a start, it must be crimped correctly, and preferably by hand. Cornish pasties have, very specifically, a side-crimp. When the little disks of pastry that form their base are folded over, the chunky join should form a half-moon along the outer-edge of the pasty. Anything else, and it's not – at least not traditionally – from Cornwall. The top pleat, pasty perfectionists like to point out, is from Devon. Cornish pasties also do not contain carrots. They contain swede or turnip, potato and onion. Not carrot. "People get very cross about that," insists Day. "Finding carrots in their pasties." And, of course, there must be meat – and there must be enough of it. At least 12.5 per cent of the filling. The art of pasty-making, it turns out, is no simple matter.

It is for this reason that I am in Callington, being shown around the Tamar Bakery. Day et al supply a variety of outlets, according to a variety of specifications, though by far the most traditional of methods – and the one that I am here to experience – is reserved for Marks & Spencer's range of hand-crimped pasties ("not just any pasties"). The production floor, a buzzing hub of oversized cooking equipment, is centred, Santa's workshop-like, around a single line of pasty-makers: overwhelmingly local, almost entirely female.

Christina Pocock is one of them. In fact, she is one of the most important, being a crimper. All of the M&S pasties that Tamar produces are hand-crimped, and having the right people to do the job is crucial. Pocock is one of 18; she has been hand-crimping pasties for more than 29 years and has, she estimates, produced some 40 million pasties in her life. She offers a particular, rather unique, brand of expertise. As she says: "You can't get hand crimpers these days." Experienced crimpers are able to seal pasties in a matter of minutes and once the product has been glazed and baked, can pick out their works based on the distinctiveness of the crimp.

Pocock is the penultimate step before the pasty goes in the oven. Prior to reaching her, the pastry has to be made and rested overnight. It needs to be cut into disks, and filled with the correct amount of filling. When the crimping is done, it moves on to be glazed with egg yolk (Tamar uses free-range only) before being placed on a tray and wheeled into the giant inferno of the Tamar oven. On the other side, a team of beady-eyed observers wait for any pasties that appear less than perfect.

Oddly for such a specific procedure, its origins lie in improvisation. The popular tale is that the Cornish pasty was created for miners. When lunchtime came, they could easily grip the crust while munching on the body. Because the tin mines in Cornwall would leave poisonous residue on their hands, the crust would be discarded. Amusing variations on the story are common: some claim that pasties would be stored down the trousers in order to keep it, and its owner, warm. A two-course pasty, meanwhile, is widely thought to have been eaten by those miners in search of something sweet: half of it would be given over to the usual meaty filling, the other half to stewed fruit.

Quite how accurate these tales are remains unclear – though there is little doubting the pasty's hallowed place in Cornish heritage; a recipe dating back to 1746 is housed in the Cornwall Records Office in Truro, and nowadays Cornish Pasty Association sales comprise some 6 per cent of the regional economy.

Back at Tamar, Pocock is showing me how to do some crimping of my own, folding the corner of the pastry over itself repeatedly until it forms a sort of rope. It take me the same amount of time to get through one as it takes her to do four. Something tells me I'll be able to pick out my own crimp pretty easily: compared to her effortless folds, mine look lumpen and uneven. The baking process, I'm told, is forgiving. It would have to be positively amnesic to make much difference in my case. Still, I'm proud of my work – it might not be quite elegant enough for Marks & Spencer, but it's certainly going to be a lovely supper.

If I'm still hungry, that is. Having tried and not-entirely-failed at crimping, I'm being rewarded with a final tasting session before returning to London. It's difficult, observes Day's team, to recreate the sensation of a pasty by the seaside when you're feeding harried families on the other side of the country. Perhaps – though there's little doubt that what I taste here, at the end of my day in the bakery, is just as good as (if not better than) that first pasty in rainy Penzance.

Though the traditional Cornish beef option is included, there is also a rather posher chicken and ham hock as well as a more radical three cheese and onion variant. Somewhat heretically, my favourite is – without doubt – the last one. It may not fall within the PGI's remit but it is delicious: the pastry hefty and butter-laden, the cheeses molten and the onion sweet.

A week after leaving Callington, when a rainstorm prompts recollections of that first Cornish holiday, I dive into Marks & Spencer to relive the experience. What can I say? At least there aren't any carrots.

Protected Geographical Indication: How to find your delicacies

Stilton Made by piercing the cheese with stainless steel needles to allow air into the core, Stilton may only be manufactured in three counties: Derbyshire, Leicestershire or Nottinghamshire. Ironically, the village of Stilton, from which the delicacy derives its name, is in Cambridgeshire.

Parmigiano-Reggiano Produced in a few specified Italian regions – Parma, Reggio Emilia, Modena, Bologna and Mantova – using grass-fed cow's milk, Parmigiano-Reggiano is an aged, unpressed hard cheese in which the only permitted additive is salt.

Champagne The term "champagne" is reserved for sparkling wines from the Champagne region in France. Carbonation comes from secondary in-bottle fermentation and production must be in accordance with stipulations from the Comité Interprofessionnel du Vin de Champagne.

Melton Mowbray pork pies Made in Melton Mowbray, Leicestershire, the pies are filled with uncured, chopped meat. The crust is hand-formed and the pie is baked free standing.

Newcastle Brown Ale After the brewery successfully applied for PGI status, Newcastle Brown Ale was restricted to being brewed in Newcastle upon Tyne. Unfortunately, in 2004, the owners decided to move their base to Gateshead – outside of the PGI's remit. The PGI was successfully appealed and revoked.