Old Fashioned
Spirit, sugar, bitters, water. The original template.
Defining structure
An Old Fashioned-type drink is built on a simple four-part formula: a spirit, a small amount of sugar, a few dashes of bitters, and dilution from stirring with ice. There is no citrus, no vermouth, no liqueur; any of those additions pushes the drink into a different family. The spirit is the whole point, lightly softened and seasoned. The technique is stirring, not shaking — the drink should be perfectly clear.
History
The Old Fashioned is the cocktail. Jerry Thomas's 1862 Bartender's Guide defined a cocktail as 'spirits of any kind, sugar, water, and bitters' — exactly this formula. Everything else is modifications of or departures from this template. The 'Old Fashioned' name arrived in the late 19th century to distinguish the original, unornamented drink from the increasingly elaborate cocktails of the era. By 1900 a Louisville gentlemen's club was serving what they called an 'Old Fashioned whiskey cocktail,' and the name stuck.
Classic examples
Other drinks in this family
Common riffs
Swap the spirit and you have a new drink: a tequila Old Fashioned, a rum Old Fashioned, a mezcal Old Fashioned. Swap the sweetener (demerara, maple, honey, piloncillo) for seasonal character. Swap or layer bitters (Peychaud's, orange, chocolate mole, tobacco) for regional riffs. The Sazerac is an Old Fashioned with an absinthe rinse and Peychaud's bitters; the Vieux Carré compounds the structure with vermouth and Bénédictine but the DNA is recognizable.