1. Crush the grapes in a shaker using a muddler.
2. Pour the rest of the ingredients in the shaker.
3. Add ice and shake vigorously for 10 seconds.
4. Double strain using a fine sieve into a glass filled with ice.
5. Garnish with a sprig of basil.

* Simple syrup is equal parts sugar and water. Dissolve sugar in a saucepan over medium heat. Strain into a sterilized jar and seal tightly with a lid.