For cucumber broth: Juice English cucumbers, sending pulp back through juicer until all juice is extracted. In a small mixing bowl, whisk together cucumber juice, simple syrup, Pernod, and fish sauce until fully incorporated. Reserve in refrigerator until ready to serve.
Put all ingredients in a shaker with a few ice cubes and shake well. Fill rocks glass with ice and pour mix over top. Garnish with a thinly cut cucumber ribbon.