The light is fading, and the dehesa is silent. Sprawling oaks fade into grey sky, and our car crawls, Jurassic Park-like, on the narrow dirt road that winds through the terrain. I look out of both sides of the car, scanning for signs of life, and then, in a flash, Maria shouts, "There they are!" I turn to match her gaze, and through the early-December murk I start to pick out black shapes in the middle distance – dark grey orbs that gain form as they converge on us, growing snouts, tails and trotters. Before long there are more than 40 pigs surrounding the car.

Maria gets out, and I follow, with a hint of trepidation. But I quickly realise these are no predators; they're plump, shy Ibérico pigs. I start to laugh as they grunt and shuffle, and I get down on my haunches to look at them up close. From what I can make out in the last of the evening's light, they're beautiful.

I'm in the south-west of Spain, having landed in Seville a few hours earlier. We've driven from Seville slightly north-west, watching the flat, arid landscape outside the city, only pockmarked by orange trees and olive groves, become lush with green vegetation, oaks and cork trees springing up in the fields that surround the road. We're in Ibérico pork country, and I've come to producer Cinco Jotas, in the historic jamón-making town of Jabugo, to see how the product goes from pig to ham.

What becomes obvious pretty much immediately, though, is the journey of Ibérico pork starts long before these glorious grey-black Ibérico pigs are taken to be slaughtered. It starts with the dehesa.

While there's no direct translation, dehesa can be loosely translated as meaning 'ecosystem', and in many ways it is the overarching symbol of the entire process. It describes not only the particular environment that Ibérico pork, most notably jamón Ibérico de bellota, or acorn-fed Iberico ham, comes from, but all the ways in which that environment works towards sustaining both itself and the pigs that graze here.

Generally speaking, the word describes hectares (one for each pig in the herd, by legal requirement for the jamón Ibérico Denominación de Origen, although the farms Cinco Jotas work with give an average of two per animal) of green grass, punctuated by large oak and cork trees, which provide the acorns that the pigs gorge on in the months leading up to their slaughter. Ibérico pigs are found in the provinces of Huelva (where we are), Extremadura, Salamanca and a handful of other regions, as well as a small part of southern Portugal, a relative stone's throw away from Jabugo.

The place is a natural larder – not just for the Ibérico pigs, but for other animals, too – cherry, fig and walnut trees are all indigenous here, and grow in abundance; and the three main trees (two types of oak, as well as the cork trees that are occasionally noticeable from bright orange flesh where their bark has been stripped) all produce acorns at slightly different times. All of these things combine to create not only the perfect environment for Ibérico pigs, but also for a hive of biodiversity and as near a perfect model for sustainable farming as you're likely to see anywhere in the world.

In celebrated chef Dan Barber's book, jamón Ibérico is referred to as "the perfect expression of the land"

To understand the dehesa is to gain an indication as to why Ibérico pork such as that produced by Cinco Jotas (which can be found in speciality food shops and Spanish restaurants around London, most notably at those of the brand's ambassador José Pizarro) is so tasty, and sold at such a premium – especially when compared to something like Serrano ham (although, in flavour terms, there is no comparison). It's why, in celebrated chef Dan Barber's book The Third Plate, jamón Ibérico is referred to as "the perfect expression of the land".

Maria Castro, the brand's director of communications, is the perfect person to show us around the environments that combine to make Cinco Jotas's celebrated jamón – the dehesa, but also the drying cellars and the town of Jabugo, which Cinco Jotas helped turn into a thriving town and one of the spiritual homes of jamón in Spain. A former biologist – who studied and lived in Seville before returning to Huelva, the province where Jabugo and many of the dehesas where Cinco Jotas's pigs are raised can be found – she has both a methodical mind and a crystal-clear understanding of almost every process that's integral to the end product.

A piece of Cinco Jotas jamón Iberico is carved

A piece of Cinco Jotas jamón Iberico is carved

From the seasonality of the dehesa, to the way exercise, space and the particular types of acorns the pigs eat convert their food to a specific combination of oleic and other acids that give the fat its rich, nutty and umami-laden flavour and complexity, she explains in scrupulous detail. She tells us about the breeding process: Cinco Jotas breeds up to eight slightly different varieties of black, 100% Ibérico pigs on its own premises, before selling them to trusted farmers, who rear them on the dehesa until they're fully grown at 20-22 months, before buying them back.

And the slaughtering process is explained, too: the pigs are used to being weighed at regular intervals throughout their lives on occasional breaks from basking, eating and wandering through the grassy, acorn-strewn fields. The final time this happens, they hop on the conveyor at an incline, as they're used to, but this time there's a higher proportion of CO2 at the top. They fall gently asleep, slide down to a separate room, and are humanely slaughtered. Minimising the stress on the animals, and a quick end, means there's no seizing up of muscles. It's part of a process characteristic of Ibérico pork, perfected over generations, in the service of both the animal and of the product.

With that, it's time for the second half of the picture – pig to plate. In Seville, before the drive up, we sampled a panoply of pork at one of the brand's eponymous tapas restaurants – from a mound of the brand's signature jamón, lush fat just beginning to turn to lardo at room temperature, to prized cuts of uncured pork, cooked as carefully and scantily as kobe beef – pluma from the neck, unctuous with savoury rendered fat, and presa, from near the shoulder, cooked like fillet steak and so succulent you could cut it with a fork.

It's at the bodega in Jabugo – the brand's headquarters – where I get a crash-course in Cinco Jotas's cured meats, though. We tour the cellars, where huge swathes of legs and shoulders hang after being buried in curing salt, and time works its magic on the very fibres of the meat and intravenous fat. A 6-7kg leg of Cinco Jotas's jamón Ibérico de bellota will set a consumer back around £500 (for the sake of comparison, you can probably find a leg of Serrano ham, made with 'any old pig', often raised on feedlots, with the curing and ageing process manipulated to take a fraction of the time, for £30).

A 6-7kg leg of cinco jotas’s jamón Ibérico costs £500

And it's not only the hectares of land and the patient, attentive process of raising them that puts on the premium – it's the maturation process, too. Each ham takes years to be ready, and loses an average of 32% of its original weight during the process. In the miles of cellar tunnels and expansive drying rooms, hams are labelled up as part of private collections – each one an investment for restaurants from Seville to London, New York and Beijing.

Walking around the cellars, it makes total sense that the brand is owned by Osborne – a group that owns a wealth of brandies, gins and wines as well as its self-titled port – and is the only food brand in the portfolio. From the sense of terroir (the unique characteristics the environment and climate has on the final product, a term usually reserved for the grapes in winemaking), the meticulous cellar-ageing, the rich history and tradition, and the whisper-quiet sense of beatification around the whole process, it has more in common with a champagne or a fine whisky than any food brand I've encountered before.

Packets of Cinco Jotas jamón Iberico

Packets of Cinco Jotas jamón Iberico

A tasting at the bodega includes three cuts from the leg, each one different in its intensity of flavour, its composition of muscle and fat. These are followed by the brand's other dried products – presa again, this time sweetly cured, lomo (loin) and the brand-new salchichón, a full-flavoured, cured sausage, which has just found its way into José Pizarro's restaurants and is now for sale at Harrods.

And with that, the picture becomes whole. A journey that begins in lush green fields filled with oaks and ends in cellars carved underneath the quaint town of Jabugo is complete, leaving the delicate processes that create and maintain it intact for the next year, and the next generation.

In Cinco Jotas's model there's the basis for a system of truly sustainable animal agriculture, intricately illustrated in a prized, luxury food product of supreme quality. While it benefits from a price point that helps preserve its tradition – and it's certainly not an everyday product for most people – it's nonetheless a shining example to a world increasingly dominated by monoculture and intensive farming. It's happy pigs. It's old oaks. It's lush grass and sweet acorns. It's salt and it's time. It's acids, muscles and fat. It's sweet, complex flavour that's as directly a product of its environment as you'll find in food. It's deliciousness, abundance, and true sustainability. It's the past and the future. It's Iberico pork, and there's nothing that can match it.