Upper crust: Why sourdough is the best bread

San Francisco's food scene is probably the most vibrant in the Americas. Whether they're starting trends or perfecting them, Bay Area chefs have long been among the world's most creative. But amidst all the innovation, there has been one faithful and beloved constant on the city's many tables: sourdough bread.

It's hard to find someone who doesn't like sourdough, but even rarer are people who know what makes it so distinctive. It's often thought to be a flavouring, or perhaps a baking technique, something pioneered in Gold Rush-era San Francisco. In fact, sourdough is simply bread in which the rise comes not from a package of shop-bought yeast, but from wild yeast that is in the air everywhere.

As the original leavened bread – all bread was "sourdough" until Louis Pasteur's germ theory led to packaged yeast – sourdough has a long and storied past. But as a let-them-eat-cake epoch gives way to home pleasures and the local food movement, sourdough is equally suited to our own times. Classic, inexpensive and uniquely local, sourdough is as fascinating to kids and novices as it is to practiced bakers and mad scientists of all ages.

Sourdough is an ancient art, but with just two ingredients its simplicity is as remarkable as its heritage. Flour and water are mixed and left to stand on a windowsill or kitchen counter. In a matter of days wild yeast take over and the mixture begins to froth and bubble with life. If you've ever wondered at the origins of this or that cooking method – "who on Earth thought to try this?" – sourdough is that rare thing, a miraculous culinary phenomenon that won't give you that feeling. With yeast naturally in the air, it's easy to imagine how an afternoon's forgetfulness in ancient Egypt led to the invention of leavened bread.

Once the "starter", as this pancake batter-like concoction is known, is up and running, its flavour can be refined over a week or more of regular "feedings" – just more flour and water. There are endless variations, but that's the gist (the Old English and modern Dutch term for yeast) of it. When you're ready to bake, there's nothing special about sourdough bread recipes except that the starter is used instead of shop-bought yeast to force the dough to rise. Meanwhile, the remaining starter will live and grow for as long as it is regularly fed.

With a little practice even a novice baker can produce something not too far from those super-tasty rolls and baguettes that tumble nightly across Bay Area restaurant tables. Nor, despite sourdough's simplicity, is there any limit to the variety of breads you can bake – everything from raisin bread to focaccia can be made with your sourdough starter, just as in the days before there was packaged yeast. And while you're baking away, sourdough offers so much else to ponder.

The starter captures the yeast in the air wherever you live, so sourdough is the ultimate food for locavores. But yeast and bacteria vary geographically, so sourdough takes on characteristics of the area where its starter is grown. That's why you'll never quite achieve that unique San Francisco taste unless you're close enough to harness the city's own Lactobacillus Sanfranciscensis. But you will make something unique to your area. So sourdough is not only the ideal local food but a classic example of terroir, the idea that local differences in soil, climate, rainfall etc produce discernible and highly prized variations in taste.

Terroir is all well and good, but if you live in an urban or polluted area you may reasonably think that conjuring up something that tastes like, say, central London, isn't a very good idea. In this case, just throw a bag of organic grapes into the mix. The yeast on the skin of the grapes will really get the party going. Or you can abandon locavorism and order a starter online from just about anywhere: France and San Francisco of course, but also Russia ("This culture is from the village of Palekh two hundred miles northeast of Moscow...") and Saudi Arabia ("the Saudi sourdough is as desert as its Bedouin baker...").

Sourdough is perfect for seasoned bakers looking to rediscover the original leavened bread. But it's also great fun for those who've never baked before, especially those who liked science class or The Little Shop of Horrors. There's something weird, bordering on creepy, about creating this living, breathing, continually regenerating pot of stuff.

It's especially bizarre if you use grapes to kick things off. The starter bubbles and gurgles, the grapes rise and fall, some days straining ominously against the plastic wrap over the bowl, other days sinking moodily to the bottom. The Frankenstein-ish aspects are particularly fascinating given that this is a culinary tradition almost as old as civilization. Endless, tasty and eerie fun for your kids and your inner mad scientist.

A sourdough starter can live forever – some in San Francisco have been simmering away since the mid-19th century. Just like traditional curry pots, with ingredients added every day but only a portion removed, your sourdough's flavour develops over time, becoming unique to you and tying your family's past meals to present and future ones. It also links your family to a natural cycle without having to go out and buy a farm; you don't even have to go outdoors. And your starter can be passed between generations or shared across them, gradually acquiring new flavours and endless variations on tradition and innovation.

Philosophers often debate how we can be the same person from day to day and decade to decade, when our molecules are constantly being replaced and memories lost or added. Are the Eiffel Tower or the Golden Gate – gracing the skylines of their respective sourdough capitals – the same even after every part has been replaced?

Somehow we think so, just as we believe that we are something more than the sum of our changing physical components and memories (even if scientists have no idea what that something might be). Ponder the contradiction between identity and impermanence while enjoying a piece of warm bread from your unique and ever-renewing sourdough starter.

Perhaps the most fascinating thing about sourdough – the main kind of leavened bread until commercial yeast arose, as it were, in the 19th century – is its links to wine. Bread and wine are the archetypal food and drink of Western civilization. And they have something literal in common as well – as noted, the surest way to make a starter is with grapes, harnessing the yeast on their skins just as vintners do.

So bread and wine are both a kind of miracle of decay, even as both are bywords for physical and spiritual sustenance. For Christians they are either a symbol of transformation or the literal stuff of transubstantiation. Even the word "Lord" is an Old English term for "loaf-keeper" ("Lady," unsurprisingly, derives from a term for "loaf-kneader"). A glass of Bordeaux at the ready, there's plenty to think about as you knead your daily bread.

Lots of baking websites advise treating your sourdough starter as a pet, which is almost but not quite as weird as it sounds: it's alive, it grows, it has specific food and environmental needs. True, it's not going to fetch a stick or doze by the hearth. But as a starter pet, as it were, it's far more interesting than a tamagotchi.

Meanwhile for parents the advantages in a recession are compelling: no vet bills, no costly pet foods (indeed you're making food), no fights over it (you can divide it endlessly), no kennel fees (just put it in the fridge). And it will never end with awkward explanations at the edge of a shallow back-garden grave: a cared-for sourdough starter will outlive us all.

I was roped into signing up for Facebook last year and it's been a decidedly mixed experience. Far more fun was setting up a Facebook account for "Sour" the starter. Registration presented difficulties – "last Tuesday" wasn't an option for birthdate, and Facebook's restrictive gender categories don't cover the relevant yeast options (a-haploid, alpha-haploid and diploid). And having a bowl of bubbling dough as an online companion (Latin: to share bread with) is admittedly a bit weird, though not nearly as odd as Gold Rush miners sleeping with their starters to keep them warm.

It's worked out quite well, though. Sour's status updates – "Sour is bubbling contentedly"; "Sour has achieved consciousness"; "Sour is now friends with Jamie"; "Sour warns, beware of the leaven of the Pharisees" – are generally much more interesting than my own. And all the limitations of Facebook-style interactions, so frustrating to me, seem to be pitch-perfect for a semi-animate bowl of frothing goop.

You can even take your starter on holiday, as we did, after dividing it into 100 ml airport-security-sized chunks that reassembled Terminator 2-like at our destination. Among our gang of friends, nearly everyone had a go at baking with it in the tiny kitchen of the holiday cottage. Tradition demanded that some wine be opened. Soon enough, the warm smells of baking filled the house, as this ancient culinary art provided for all the friends I'd still be breaking bread with had Facebook never been invented.

Getting started: First steps to sourdough

Day one: The success of establishing a starter depends on the room temperature. About 30C is ideal for yeast activity, but 20C will do. Clean a large transparent glass jar and spoon with boiling water. Add 50ml water, 35g white flour and 15g rye flour to the jar, stir, and leave for 24 hours (covering is optional).

Days two and three: Repeat these steps, to add to the mixture, and leave again.

Day four: Throw most of the mixture away, leaving about 1 tbsp of starter in the jar. Add 100ml water, 70g white flour and 30g rye flour, stir and leave for another 24 hours.

Day five: Repeat these steps.

Day six: The starter should have increased in volume by about a third, and bubbles will be evident. Repeat the steps for Day four.

Day seven: Repeat the steps for Day four for at least another week. When the mixture doubles in volume, has surface froth and plenty of bubbles after being left for the 24-hour period, it is ready for baking.

Cover your starter and store in the fridge. Each week, take it out of the fridge and repeat the steps for Day four to keep it active.

For more tips and information go to: www.sourdough.com

Enjoli Liston