1: In a glass, combine the brown sugar and mint, and mash them well to release the mint's flavor.
2: Add the lime juice and continue mixing with the pestle together with the sugar and mint.
3: Add crushed ice cubes and a few drops of Angostura (if available), along with the white rum and sparkling water.
4: Stir quickly with a straw and serve with a slice of lime and a few fresh mint leaves.
