Unknown origin | 1880s
Briefly dry shake, then shake again with ice:
1 egg white
3/4 oz simple syrup
3/4 oz lemon juice
2 oz bourbon whiskey
Express lemon oil over
Garnish: Angostura bitters décor & cherry
Variation: Float 1/4 oz red wine and skip the Angostura bitters for a New York Sour.
Jerry Thomas first covered Whiskey Sours in his 1862 book "The Gentleman's Companion" and just about every cocktail book since then has featured a version of the classic spirit/lemon/sugar combo. I've read a baffling array of recipes called "Whiskey Sour" - tall with soda in a Collins glass, frappe-style with blended crushed ice and Angostura bitters in a fizz glass, whiskey-forward on the rocks or up in a cocktail glass, and more. During the cocktail renaissance of the early 2000s, craft bartenders rediscovered the Boston Sour, an up variation shaken with egg white to create a silky, thick foam on the top. Many called it the "Traditional Whiskey Sour," but its "Boston" moniker has a long legacy in print, in spite of its hazy origin.
Egg whites in a cocktail might sound a little freaky at first, but it won’t take more than a sip to change minds. They become a finger-dipping dessert at the end... but be aware of the faint “wet dog smell.” A quick spritz of citrus oil and a touch of bitters will handle that.