In a cocktail shaker (or flat bottomed drinking glass), add 8-10 mint leaves and 3 sugar cubes. If desired add 2-3 dashes lime bitters.
Use a muddler to crush the sugar and mint together. Muddle until sugar has dissolved.
Add 1 oz fresh lime juice to shaker. Add 1/4 cup fresh mango chunks. Light crush and muddle mango into the drink.
Add 2 oz light (white) rum of choice.
Fill serving glass with ice. Pour cocktail into serving glass. Add 2 oz club soda. Serve with fresh mint and garnish with a slice of mango.