All that is needed is a banana.
The banana needs to be frozen rock solid for this to work. Spark is making sure ours is frozen, only a boy would think of this. A word to the wise here is to peel the banana before freezing it or you have to whittle the peel off after it is frozen.
Chop it up and give it a few spins in the food processor. Adding a tablespoon of very cold water after it is mostly chopped makes it turn into ice cream faster.
The consistency is just like ice cream. Spark loved it and Dancer had a little, tiny bite and agreed that it was the same as ice cream. She doesn't like bananas, I think I fed her too many as a baby, so Spark got to enjoy the whole bowl.