Which cocktail is traditionally made with bourbon, lemon juice, simple syrup and an egg white?

The cocktail traditionally made with bourbon, lemon juice, simple syrup and an egg white is the Whiskey Sour.

A standard Whiskey Sour combines whiskey, fresh lemon juice and sugar or simple syrup. When egg white is included, the drink is sometimes called a Boston Sour, although many modern recipes use the names inconsistently. The egg white creates a smooth texture and a foamy cap when shaken thoroughly.

The Whiskey Sour appeared in print during the 19th century, including in Jerry Thomas’s 1862 Bar-Tender’s Guide. Early sour formulas followed a broad pattern: a base spirit, citrus juice and a sweetener. Whiskey became the defining spirit in this version, while bourbon is now especially common in the United States.

The New York Sour adds a float of red wine, and the Gold Rush omits the egg white and uses honey syrup. Those variations are related but are not the classic egg-white preparation.