This simple variation on the cocktail famously associated with Compton, California is a breeze to mix, and a surefire hit at any party. Begin with 2 ounces of Juniper Green Gin in a shaker with ice. Add 1.5 ounces of organic grapefruit juice and stir. Pour into a lowball glass and top off with soda. Slap a sprig of rosemary (place it in your palm and smack it with your opposite hand to crush the leaf slightly, releasing the aromatic oils) as a garnish.