Roughly chop the cucumber, no need to peel, and blend with a small splash of water until smooth, then strain through a fine sieve. One cucumber gives you about ¾ cup, enough for a few rounds of cocktails.
Add the cucumber juice, gin, lime and simple syrup to a shaker with ice, along with a pinch of flaky salt. Shake until cold and strain into an ice-filled glass. Top with sparkling water, stir gently, and garnish with a cucumber ribbon and a sprig of mint and basil. For the non-alcoholic version, use NA gin or just leave it out and add a little more cucumber juice.
