If you don't have bottled cucumber juice, peel (optional) and roughly chop a small cucumber. Pulse in a blender until liquified, then strain through a fine mesh sieve or cheesecloth into a bowl, pressing to extract about 0.5 oz (15 ml) of juice per serving. Discard solids.

Dry shake (if using egg white)

Add 0.5 oz egg white to a cocktail shaker along with gin, lime juice, green Chartreuse, simple syrup and cucumber juice. Seal and shake vigorously without ice for 15 seconds to emulsify and build foam.

Wet shake

Add 6 ice cubes to the shaker (on top of the dry-shaken mix if you used egg white). Shake hard for 12–18 seconds until the shaker is cold to the touch and properly diluted.

Strain and serve

Double-strain the cocktail into a chilled coupe or a rocks glass filled with 1 cup fresh ice (your preference). Use a fine-mesh strainer in addition to the shaker strainer if you used egg white or fresh cucumber juice to remove any small solids and to ensure a silky texture.

Garnish

Thread a thin cucumber ribbon or place a cucumber wheel on the rim or float it on the surface. Express a lime twist over the drink and drop it in if using. Optionally, slap the mint between your palms to release aroma and rest the sprig on the cucumber ribbon or rim.