• 3 ounces Coruba dark Jamaican rum (if you can't find Coruba, substitute another dark, heavy rum)
• 1 ounce simple syrup (equal parts sugar and water, mixed until dissolved)
• 3/4 ounce fresh lime juice
• 3 dashes Angostura bitters
Combine ingredients in a tall glass and fill with crushed ice. Swizzle with a bar spoon until a frost forms on the outside of the glass. The ice will settle as you do this; add more crushed ice to fill, garnish with a mint sprig.