The genie that is palo cortado is unbottled in a visit to three bodegas in Spain. Geoffrey Gray investigates.

Among high-end sherries, palo cortado is a mystery. A century ago, perhaps longer, tasters would check on the casks to ensure that the sherry inside fell into its proper category. Was it the lighter manzanilla or fino? The drier amontillado? Or the darker oloroso?

Occasionally, sherry noses stumbled on a wine that was none of the above. Unable to classify it, the tasters marked the barrel with two slashes of chalk. This palo cortado ("cut stick") meant the barrel could not be sold, and the wine inside was often tossed.

What a pity, many sherry-makers thought. That a sherry could not be defined did not make it a bad sherry. So many bodega owners decided to keep a few barrels around for limited sales or for personal use. The sherry was appealing in its enigmatic way. It refused to be defined with its own rebellious spirit, much like the sherry-makers themselves.

Their bodegas are concentrated in a region called the Sherry Triangle, demarcated by three cities in southern Spain. The tradition for many there is to drink as many as eight glasses of sherry a day, starting at noon, often earlier.

Locals go to the bodegas with plastic jugs and have them filled with the lighter and younger manzanilla or fino for only a few euros. In contrast, palo cortado is hard to find and can retail for upward of 40 euros per bottle ($52) and higher, a price point that is out of reach for daily sherry drinkers.

There are bodegas that serve it, though, or will plunge their tasting canes into their private barrels to indulge the curious and thirsty. While many palo cortados out there are merely different sherries mixed together, and aren't considered pure by aficionados, some bodegas have been in the business of making the real thing for more than a century. Below are three who opened their doors to a visitor.