Whisk together the water, sugar, cocoa, and salt in a large saucepan on a high heat.
Bring mixture to a boil ensuring that you keep whisking frequently. Continue to boil (and whisk) for another 1 minute.
Remove the sorbet base from the heat and mix in the chocolate until melted, then add vanilla.
Add the mixture to a blender for about 20 seconds until nicely combined and smooth in consistency.
Pour mixture into an airtight container and cool in the fridge for a few hours or overnight if you have time.
Churn sorbet in ice cream maker as per manufacturer's instructions. Once complete, add to a container and freeze until hardened.
