I saw this posted by multiple people on Pinterest. I tried it out and was amazed that it actually worked! Here is the site I referenced.
Bananas, extra ripe (We used 4)
Peel the bananas and slice into 1/2 inch thick slices. Lay on a cookie sheet lined with waxed paper. Freeze for a few hours.
Pop them into a food processor or blender. (We used a food processor.) Keep pushing the bananas down with a spatula. At first, the bananas will just look liked chopped bananas and you will doubt that this will really work. Just keep scraping down the sides and as you continue, it will get more and more like ice cream. If you eat it immediately, it will be more like "soft serve"...which is the perfect opportunity to add some mix-ins like chocolate chips or peanut butter (or both). Pop it in the freezer to eat later and it will be a more traditional, harder ice cream.
Our girls enjoyed it topped with Magic Shell...(tasted like a chocolate covered banana). YUM! Such a fun & healthy treat.