Makes approximately 1 quart (32 oz.)
7½ oz. light rum (preferably Cruzan or any neutral white rum)
5 oz. watermelon juice, or 4 one-inch slices
3¾ oz. fresh lime juices (about three limes)
3¾ oz. black-mint simple syrup (see recipe below)
½ tsp. kosher salt (optional)
Black-Mint Simple Syrup
Makes approximately 2 cups
½ cup granulated sugar
½ cup water
3 to 4 sprigs fresh black mint (if you can't find black mint, use regular green mint and double the number of sprigs)
For Syrup: Place all ingredients in a medium saucepan over medium heat. Stir just until sugar dissolves. Remove pan from heat and cover. Set aside to steep and cool, approximately 1 hour. Strain and discard mint. Store in the refrigerator until ready for use.
To Assemble Cocktail: Place all ingredients in a pitcher half filled with ice. Stir vigorously for about 2 minutes, until ingredients are very well chilled. Fill the rest of the pitcher with ice. Pour into individual highball glasses filled with ice. Garnish with a lime wheel and/or a sprig of mint.