Simple Syrup: In a small saucepan, bring sugar and water to a boil. Simmer until sugar is dissolved, about 3 minutes. Remove from heat. Cool completely. Keep extra in refrigerator in glass jar for up to one month.

Put 4 mint leaves in a cocktail shaker and press gently with a muddler or wooden spoon. Add the gin, grapefruit juice, lime juice and simple syrup to the cocktail shaker.Fill with ice, cover and shake vigorously. Strain to chilled coupe. Garnish with mint leaf.