Before you begin, find a baking tray fits into your freezer. Cover the baking tray with baking paper or tinfoil. This will make the banana easier to remove once frozen.
Peel your bananas, then slice into bite-size pieces and lay them out in a single layer on the baking sheet. A quick note on knives here – I've allowed Small Child to use a small sharp knife under close supervision for some years now. I believe that teaching your child to use a knife safely is preferable to keeping them away from the altogether, but it really does depend on the individual child – use your judgement to decide whether your child is ready to use a knife. With this recipe, a blunt butter knife will also work just fine on banana.
Place the baking sheet in the freezer and freeze overnight or until the banana slices are frozen solid. If you're not going to make the ice-cream immediately, you can pop the banana pieces into an air-tight bag once frozen and return to the freezer until ready to use.
Once you're ready to make the ice cream, remove the banana slices and throw them into a blender or food processor. Whizz up immediately. You might find that the banana first breaks up into a crumbly texture but be patient and continue to blend it until it goes smooth and creamy.
Scoop the ice-cream out of the blender and stir in the chocolate chips. Serve immediately.
You might find the ice-cream goes a little melty (as ours did when I stopped to take photos of it!), in which case you can return it to the freezer for a little while to harden up.