Swing into summer with this subtly watermelon sour. You can increase the watermelon flavors by using melon liqueur or vodka. But leave it mysterious by sticking to watermelon simple syrup.
Combine ingredients to a cocktail shaker and add ice. Shake until very cold, then shake another 30 seconds. Double strain into a chilled coupe glass and garnish with fresh watermelon and mint leaves.
Notes
If you have watermelon vodka, the base spirit should be split in half between whiskey or vodka and the watermelon vodka.**See link above for watermelon simple syrup