Preheat the oven to 180C/350F and line a large baking tray with baking paper, and set aside.
In a large mixing bowl, combine the bananas, oats, and peanut butter and mix very well. If the batter is too thin, add more oats. Fold through chocolate chips if using them.
Using your hands or a cookie scoop, form into 12 balls and set them on the lined baking tray. Press each ball into a cookie shape and bake for 10-12 minutes, or until slightly firm on the edges, and remove. Allow to cool on the tray completely.
Notes
TO STORE: Store the cookies in a sealable container in the refrigerator, or on a plate, covered in plastic wrap. Flourless banana bread cookies will keep for 5 days.TO FREEZE: Wrap the cookies in parchment paper and place them in a ziplock bag or freezer-friendly container. Cookies will keep well frozen for up to 2 months.