1 cup dried rosella calyces
1 L water
½ bunch fresh mint (optional)
Fill a pot with 1 L of water and add the hibiscus flowers. Bring to a boil, then lower the heat, add the mint leaves (optional) and cook for 5 more minutes.
Filter the infusion obtained, add the sugar, mix, taste and possibly rectify by adding a little more water or sugar. Let cool.
Pour the juice in a plastic tray or cake tin. Place in the freezer for about an hour.
Once you notice that the liquid is solidifying, remove and break up the ice crystals that have formed using a fork. Return to the freezer and repeat after an hour one or two more times, depending on the preferred size of your ice crystals (larger or finer).
If you prepare the granita in a large dish, the preparation time will be much shorter, so be careful that the mixture does not completely freeze.
Serve the crushed ice in small glasses and eat immediately.
Notes: You can flavour the rosella juice with pineapple instead of mint leaves.