How to Make It
In a cocktail shaker, combine the Basil-Cucumber Puree, lime juice and salt. Fill the shaker with ice and shake well. Strain into a chilled, ice-filled double rocks glass and stir in the tonic water. Clap the basil leaves between your hands over the drink to release the essential oils and add them to the glass.
Basil-Cucumber Puree: In a small saucepan, lightly toast 1 teaspoon coriander seeds over low heat until fragrant, about 3 minutes. Transfer to a blender. Add 1 large peeled and seeded English cucumber and 1/3 cup basil leaves; puree until as smooth as possible. Refrigerate for up to 1 day. Makes about 10 ounces.