The Cinq à Sept is a holiday cocktail that was created by author Jassy Davis and was first published in her book Winter Warmers: 60 Cosy Cocktails for Autumn & Winter. It uses the Gin Sour template by pairing the classic's dry gin, lemon, and simple syrup with frothy egg white, herbal Yellow Chartreuse, and flavorful tonic bitters.
Add gin, lemon juice, simple syrup, Yellow Chartreuse, egg white, and tonic bitters to a shaker.
Fill shaker with cubed ice.
Shake for 10-20 seconds.
Using tongs, remove ice from shaker.
Dry shake for 5-10 more seconds to emulsify egg.
Using a Hawthorne strainer, strain into a coupe glass.
Garnish with lemon twist.