(n.) A fortified wine of 15 to 22-percent alcohol by volume made in the Jerez region of southern Spain, sherry comes in a range of styles from lean and light in weight to sweet and viscous, plus a bit of everything in between. Prized by sommeliers and bartenders for its versatility in both food pairing and cocktail making, sherry has, in recent years, roared back from afterthought to cornerstone of forward-thinking bar programs. But don’t call it a fad, though: sherry has been around for over three thousand years.

The process of making sherry begins with adding a mixture of grape brandy and aged wine (called mitad y mitad) to a light wine. If the wine is fortified to around 15-percent alcohol, a layer of yeast called flor will form over the liquid as it ages in barrels, protecting it from oxidation. This process is called “biological aging.” Styles of sherry that age almost exclusively under the layer of flor are called fino or manzanilla and are generally light, crisp and salty.

If the wine is fortified to 17 percent or more alcohol, the flor cannot develop and the wines oxidize as they age in barrels, forming oloroso sherry, which, though still dry, has a rich, nutty and caramelized character. Amontillado and palo cortado sherries begin with a layer of flor that dissipates during aging, forming a hybrid between the biological and oxidative styles.

Sweet sherries fall into two categories: naturally sweet and blended. The two naturally sweet wines of the Sherry region are Pedro Ximenez, often abbreviated as PX, and Moscatel, both made from fermented, dried grapes.

Blended sherries are generally a mixture of sherry—generally oloroso for cream or medium blends, and fino for pale cream—and either PX or concentrated grape must.

A key component of sherry production is the solera system, in which young wines are slowly introduced to older wines via a system known as “fractional blending,” because it occurs over the course of many years. The newer vintages are used to top off the barrels holding medium-age vintages, which are in turn used to top off the old vintage barrels as sherry is withdrawn for bottling. Major bodegas (sherry houses) will use multiple solera systems, many of which can contain anywhere from less than ten barrels to more than 20,000.

As of 2000, sherries may be classified as either V.O.S. (Vinum Optimum Signatum or Very Old Sherry) for wines over 20 years old and V.O.R.S. (Vinum Optimum Rare Signatum or Very Old Rare Sherry) for wines over 30 years of average age. And though vintage-dated or añada sherries are far less common than they were in the 19th century, some houses still bottle wines from a single vintage.

Dry sherries are typically consumed as an aperitif alongside salty snacks, but they are also making further inroads with sommeliers who appreciate their versatility with food.  The return of sherry to the barman’s repertoire has also furthered its growth in the United States. A few producers worth seeking out: Valdespino, El Maestro Sierra, Gutierrez Colosia, La Guita, Equipo Navazos, Fernado de Castilla, Lustau, Hidalgo-La Gitana and Emilio Hidalgo.