3/4 cup crushed ice
1 1/2 ounces aged Jamaican rum
1 1/2 ounces gold Puerto Rican rum
1 ounce 151-proof Lemon Hart Demerara rum
3/4 ounce freshly squeezed lime juice
2 teaspoons white grapefruit juice
1 teaspoon Cinnamon Syrup
1 teaspoon Grenadine
1/2 ounce falernum
1/8 teaspoon Pernod
1 dash aromatic bitters, such as angostura
1 mint sprig
Place all ingredients except ice cubes and mint sprig in a blender. Blend on high until frothy but not slushy, no more than 5 seconds.
Pour into a tall, narrow glass and add ice cubes to fill the glass. Garnish with a mint sprig.