01 - Combine watermelon cubes, lime juice, and sugar in a blender. Process until completely smooth, ensuring no chunks remain.
02 - Taste the mixture and add additional sugar if needed. If incorporating mint, stir in the chopped leaves until evenly distributed.
03 - Transfer the mixture to a shallow, freezer-safe baking dish. Spread evenly and freeze for approximately 90 minutes.
04 - Remove from freezer and vigorously scrape the surface with a fork to break up forming ice crystals, creating a grainy texture.
05 - Return to freezer, then repeat scraping every 30 minutes for 3 to 4 hours until the mixture reaches a light, fluffy consistency throughout.
06 - Spoon the granita into chilled glasses or bowls. Optionally garnish with additional fresh mint or lime zest before serving.