Place the watermelon into a blender and blitz until it is liquid. Strain the watermelon through a fine sieve to remove the pulp. Add the sugar, lime zest and juice to the strained watermelon juice and stir until the sugar has completely dissolved. Pour into a freezer-safe dish and place uncovered into the freezer. Stir the mixture twice during the first 2 hours of the freezing process to break up the ice crystals, then leave overnight to freeze to solid.

To Serve

Arrange the shucked oysters onto a serving platter. Use a fork to scrape the granita into fine shavings then place a generous teaspoon on top of each oyster. Top with a pinch of chilli flakes, lime zest and micro greens if using. Serve immediately.