2 oz of Dark rum
1/2 oz of sugar syrup (or simple syrup)
2 oz of soda water
4 of mint
2 dash of Angostura bitters
Squeeze lime juice into a highball glass. Add the shell, fill with crushed ice and add the mint. Pour in the rum, angostura bitters and sugar syrup. Swizzle until glass frosts. Add the soda, garnish with a sprig of mint, and serve with a straw.