01 - Combine watermelon chunks, mint leaves, lime juice, and sugar in a blender or food processor.
02 - Blend until the mixture is completely smooth. Taste and add more sugar if desired.
03 - Pour the purée through a fine mesh sieve into a shallow, freezer-safe dish to remove pulp for an extra smooth texture.
04 - Freeze for 45–60 minutes, then scrape the edges with a fork to break up any forming ice crystals.
05 - Return the dish to the freezer. Every 30 minutes, use a fork to scrape and fluff the mixture, repeating 3–4 times in total, until fully frozen and the texture is light and crystalline, about 4 hours.
06 - Fluff the granita with a fork and spoon it into chilled glasses. Garnish with fresh mint leaves and serve immediately.