Sherry is a fortified wine made in the "Sherry Triangle" -- the villages of Sanlucar de Barrameda, Jerez de la Frontera, and El Puerto de Santa Maria, in southern Spain. Sherry is always made from white grapes, and is always fortified with brandy after primary fermentation. The differences between the styles of Sherry come from the aging processes the wines undergo. Sherry can range in style anywhere from bone dry to incredibly rich and sweet, and anywhere in between.
Wine production in and around Jerez probably dates back 3,000 years, but Sherry as we know it today began when the Moors conquered the region in 711 and introduced distilling technology. Sherry became popular in England after Sir Francis Drake captured nearly 3,000 barrels of Sherry in the sacking of Cadiz in 1587. In 1933, Sherry was the first D.O. (Denominacion de Origen) - a wine making region protected and regulated by Spanish law.
There are three grapes and three soil types in the Sherry growing region. The grapes are Palomino (the finest, and used in most Sherries), Moscatel (which is Muscat, and provides aroma), and Pedro Ximinez, which is the source of arrope, the syrup used to sweeten Sherry.
Each grape has a corresponding soil type in which it grows best: Albariza (a white, chalky soil) makes fine Palomino. Barros is heavier, dark brown, and has clay inclusions. Pedro Ximinez grows well there. Finally, there is Arenas, a yellowish soil with a lot of sand, is suited for Moscatel. By law, 40% of the grapes used in any Sherry must come from Albariza soils.
The divisions of Sherry can be quite confusing, but each type follows from one another. Grapes are crushed and fermented dry. Some of the Pedro Ximinez harvest is not fermented, but boiled down into the thick, sweetening syrup called arrope. Once primary fermentation is finished, the young wines are graded, with the best going into the reductive program. These wines are the lightest, most delicate, and most aromatic. The wine is lightly fortified with brandy to around 15.5% abv, put into barrels that are 5/6 full, and watched carefully for the development of flor, which is a yeasty scum that develops in some barrels and protects the Sherry from oxidation and lends its own aromas of cheese and vinyl shower curtain. Flor also consumes the wine's acidity, and produces aldehydes. The product of this process is called Fino sherry. Fino sherries that come from the town of Sanlucar de Barrameda are called Manzanilla.
In some barrels, the flor never develops, or dies. These barrels are fortified a bit more (flor can only live in wines up to about 16% alcohol), and are called Palo Cortado. This is a rare style, and is halfway between Fino and Oloroso, and often collapses into the Oloroso style.
As Fino sherries age, they begin to oxidize slowly in their barrel. There are a series of intermediary steps (FInos become Fino-Amontillado, then Amontillado-Fino) before arriving at the next type - Amontillado sherry. This aging process between Fino and Amontillado usually takes eight years.
Taking a step back, if the finished wine is judged to be coarser or less desirable after primary fermentation, the barrel is put into the oxidative process. The barrels are fortified to 18% alcohol to stop the growth of flor, and are put outside to cook in the 100 degree summer heat until they turn brown. After this process, these wines are known as Oloroso, and are dry. Some Oloroso sherries are sweetened with arrope, and become Cream sherry.
Finally, Moscatel and Pedro Ximinez sherries are made from partially raisined grapes, and the fermentation process is stopped early in order to preserve the sweetness of the wines. They are then left to oxidize like Oloroso.
The great majority of sherry is made through the solera system. This involves tiered stacks of barrels called criaderas. Between 10 and 35% of the wine in the oldest barrel in the solera is removed for bottling. Wine is then moved from the next youngest barrel into the older one, all the way back to the youngest barrel in the chain, which is filled with new wine. The solera system guarantees consistency and complexity in sherry production. Most soleras have between a dozen barrels and hundreds - if a mark like 1/47 is on a sherry label (and it should be on more expensive sherries), that means there is one criadera of 47 barrels in this particular sherry's solera.
In the early 2000's, the Consejo Regulador (regulatory council) for the Jerez region began to classify some sherries as aged, with the letters VOS (Vinum Optimum Signatum) and VORS (Vinum Optimum Rare Signatum) to denote a amontillado, oloroso, palo cortado, or Pedro Ximinez sherry with either 20 or 30 years of age respectively. These special sherries are expensive, and as they've proven popular, a new age dated 12 and 15 year old Sherry style has been announced. A very rare style, called añada is reserved for vintage dated sherries. Lustau is one producer who makes a 1990 vintage Oloroso Sherry.
Sherry is one of the world's great wines, and certainly one of the least well known. Lighter styles of sherry like Fino, Manzanilla, Amontillado are great as an aperitif, typically with cured meats, olives or almonds. Medium bodied sherries like Palo Cortado and Oloroso can be served at the table - Palo Cortado and authentic paella being a particularly inspired match. Desserts, cheeses, ice cream, or dried fruits are natural pairs for Cream, Moscatel or Pedro Ximinez sherries.
In cocktails, Sherry can lend oxidative notes to drinks, and plenty of complexity. Many old cocktail recipes call for Sherry.