Peel and chop the bananas into rounds, then lay them out on lined baking tray and freeze overnight until solid.   If you’re not going to make the ice-cream immediately, you can pop the frozen banana pieces into an air-tight bag and return to the freezer until ready to use.

Once you're ready to make the ice cream, throw the banana pieces and frozen blackberries into a high speed blender and whizz them up together until smooth.  You'll probably find that the fruit breaks up into a crumbly texture and you need to scrape down the sides several times, but be patient and continue to blend it until it goes smooth and creamy. Taste the mixture and add maple syrup or honey to taste if needed. This will really depend on the ripeness of both the bananas and blackberries - the riper they are the sweeter it will be.

Once smooth, serve immediately or pop into a cake tin or plastic tub and return to the freezer until ready to serve.