Steps
1. Muddle the mango cubes, lime quarters, mint leaves, and brown sugar in a glass until thoroughly combined and fragrant.
2. Fill the glass with ice cubes.
3. Pour the white rum over the ice and muddled mixture.
4. Top off with club soda and stir gently to combine.
5. Garnish with a mint sprig and a slice of lime if desired. Serve immediately.