The London-Style South Side Royale was invented by Julie Reiner, co-owner of the Flatiron Lounge in Manhattan and Clover Club in Brooklyn. This easy-to-prepare cocktail makes for good party-friendly fare. It’s so light and bright that it almost seems … healthy! We like to float a thin slice of cucumber on top to further the illusion of healthfulness.
In a shaker, muddle the mint leaves with the cucumber and simple syrup. Add the gin, lime juice, and several cubes of ice and shake vigorously for 15 seconds. Strain into a champagne glass. Top with about 1 1/2 ounces of champagne.