1. Drop the mint leaves into the bottom of a sturdy glass and cover with 1 ounce of rum. Let it sit for 1 minute to allow the mint leaves to soften.
2. Using a muddler or the handle of a wooden spoon, coarsely muddle the mint leaves so that they are broken into large pieces.
3. Add 1 ounce mango puree and stir vigorously.
4. Drop 3 to 4 ice cubes into the glass, then top with lime sparkling water.
5. Garnish with mint sprig and serve.

Makes 1 cocktail.