- In a blender, purée the cucumber until smooth. Place a fine sieve over a bowl and pour in the cucumber purée. Cover and let drain, without pressing on the pulp, for 1 hour in the refrigerator. Compost the pulp. Save the juice. You should obtain about ¾ cup (180 ml) cucumber juice (see note).
- Place the ice in a tall, cold glass. Add the cucumber juice, gin, lime juice and cane syrup. Mix. Top off with the tonic water. Garnish with the mint and cucumber slices, if desired.
The cucumber juice will keep for 3 days in an airtight container in the refrigerator.