To make the hibiscus syrup: Boil 2 qt. water, dried jamaica leaves, and sugar in a large pot over high heat. Lower to a simmer then stir until sugar is completely dissolved. Strain into a sealable container. Refrigerate.
To make the cocktail: Muddle one mint spring in the bottom of a glass. Set aside. Combine all ingredients except mint in a shaker tin. Add ice and shake until frost starts to form on the outside, about 5-10 seconds. Strain through a Hawthorne strainer into the glass. Add fresh ice and muddled mint. Garnish with fresh mint.