MAKES 1 COCKTAIL
Origin: Little Branch, N.Y.C. / Classic American Sours refer to any cocktail with citrus, sugar, and a spirit. But the traditional sour includes an egg white and often a garnish of bitters. In a cocktail shaker, combine 1 large egg white, 1 ounce applejack, 1 ounce rye whiskey, ¾ ounce fresh lemon juice, and ¾ ounce simple syrup and shake vigorously for 10 seconds to emulsify. Fill the shaker with ice and continue shaking until it feels frosty, another 10–15 seconds. Strain into a sour glass and serve immediately.