Preheat the oven to 350 degrees F (180 degrees C).
Mash the bananas with a fork and measure out 1 cup. It is important to measure this out to ensure that the batter consistency is correct.
Add the mashed banana, peanut butter, egg, cinnamon, and baking powder to a bowl and mix until well combined. It's completely okay if there are chunks of banana in the mixture, they will soften fully once baked.
Fold in the chocolate chips until incorporated.
Scoop out tablespoon-sized portions into a silicone mini muffin pan (or greased metal muffin pan) and sprinkle some extra chocolate chips on top if desired.
Bake for 15 minutes, or until a toothpick inserted comes out clean. Allow the muffins to cool completely before serving.
