For the Cucumber Vinegar:
1/2 cup sliced cucumber (peel on)
1 cup unseasoned rice wine vinegar
For Each Drink:
2 shiso leaves, plus 1 extra for garnish
8 mint leaves
1/4 ounce simple syrup (see note)
3 ounces fresh Granny Smith apple juice (see note)
1 ounce Cucumber Vinegar
1/4 ounce fresh juice from 1 lime
For the Cucumber Vinegar: In a small bowl, combine cucumbers and rice wine vinegar. Let stand 5 minutes, then strain. Reserve Cucumber Vinegar for cocktails, and serve cucumber slices as a snack, if desired.
For Each Drink: Add shiso, mint, and simple syrup to a highball glass. Muddle, pressing gently, until mint fragrance is noticeable; do not tear or mash the leaves. Add apple juice, cucumber vinegar, and lime juice and fill glass with ice. Stir until well chilled, about 10 seconds. Garnish with shiso leaf and serve immediately.