Bourbon, fresh lemon, and simple syrup — the foundational sour cocktail. Add egg white for the Boston Sour.
The Whiskey Sour is one of the five foundational cocktail templates — Sour, Spirit-Forward Stirred, Highball, Sparkling, and Flip — from which most other cocktails derive. The formula (spirit, citrus, sweetener) dates to at least 1862 when it appeared in Jerry Thomas's 'Bartenders Guide'. It predates many of the cocktails it influenced.
The Boston Sour (with egg white) transforms the texture significantly — from a straightforward, slightly thin sour to a silky, pillow-topped drink. The egg white adds no flavour but creates a foam that makes the drink feel more substantial and allows garnishes (particularly Angostura bitters drops) to rest on the surface. A Whiskey Sour without egg white is correct; with it, it's better.
Float ½ oz dry red wine over the completed Boston Sour. See our full New York Sour recipe.
Replace bourbon with rye whiskey. The pepper and spice of rye makes the citrus more assertive and the drink drier.
Add 1 oz fresh orange juice alongside the lemon. The orange softens the tartness and makes the drink more approachable — a common bartender modification.