There’s a way of making wine in Spain that produces a flavoursome, mature taste. Just don’t call it shh..

Here’s the challenge: can I write a complete column without mentioning the sh.... word? There are plenty of more specific alternatives: familiar fino or manzanilla, less obvious oloroso or palo cortado.

So, where are we? In that particular triangle of south western Spain cornered by Jerez de la Frontera, El Puerto de Santa Maria and Sanlucar de Barrameda, where the soils are chalky white, the predominant grape is palomino and the weather is much influenced by the powerful currents of the Straits of Gibraltar, bringing welcome humidity on westerly winds and unwanted arid dryness if the direction is easterly.

There is a particular style of wine-making here which is unique in the world. White wines are made conventionally, fortified with grape spirit to a maximum 15 degrees alcohol, then matured in not-quite-full old oak barrels, developing a surface layer of natural yeast which works quite remarkable transformations.

That last process is known as biological ageing, as opposed to the traditional oxidative ageing which the majority of the world’s older wines undergo. In biological ageing the yeast eats up alcohol and sugars, so the alcohol level reduces rather than increases as time passes and the wines become drier and drier.

They have a strange pungency, sometimes nutty, sometimes salty, sometimes with hints of fresh apple or dried fruits. By the time they’re bottled, even the youngest are several years old: they progress through a regulated stack of barrels, youngest wine on top, oldest at the bottom. As wine from that bottom line is drawn off for bottling, the barrels are replenished from the line above, which in turn is topped up from the next one up, with the topmost refilled with the new vintage wine – the solera system.

Tasting through the styles which result, manzanilla is first up. It matures in the bodegas of Sanlucar de Barrameda, right by the water’s edge, its characteristic salty flavour due to that maritime influence – the makers leave the bodega windows open so the sea breeze can drift it.

Fino, though made in the same way, hails from a few miles inland, at Jerez de la Frontera, where it’s hotter and drier: the bodegas are misted to keep up humidity. Finos are a touch warmer and fuller, but, like manzanilla and the other wines in this complex sequence, certainly should not be regarded solely as aperitifs. They are among the very best partners for a wide variety of food.

These pale wines have darker relatives, the olorosos. Both come from the same vines, by the same wine-making process, but are separated early on: the lighter, drier base wines are destined for fino/manzanilla, the heavier ones for oloroso.

There are other darker wines, too, direct descendants of fino. Dry amontillado happens as the flor yeast dies away. Deeper flavours develop, with greater complexity but still a natural freshness.

Back to olorosos: at the first classification, these are fortified to 17 degrees, an alcohol level too high for yeast formation. They age to glorious amber and topaz colours, and rich nuttiness of taste.

There’s another category which emerges at a second classification. Certain finos are identified as having extra potential and are refortified up to the 17 degree oloroso level. They are the rare and special palo cortados, though last month’s biggest-ever UK sh.... tasting showcased a remarkable number of them.

It’s not difficult to find very fine examples in all these categories, and prices are often way below that merited by their quality and complexity.

Next week – if you haven’t worked it out already – I’ll spell out the sh.... word and identify just some of the many examples which truly are worth buying.