Mix mashed banana, peanut butter, honey, vanilla, and eggs using a hand mixer in a medium bowl. Make sure that you use a full cup of mashed banana and measure that first.
Add dry ingredients and blend with hand mixer while scraping the sides of the mixing bowl until just mixed together. Do not overmix! Stir in chocolate chips (optional).
Spray muffin tin with cooking spray or line with muffin wrappers. Spoon batter into prepared muffin tin, filling each cup almost to the top.
Bake for 15 to 17 minutes until muffins are cooked through. Don't over bake or they'll be dry! Let cool in the muffin tin for 10 minutes and then remove and let fully cool on a wire rack.
Notes
* While oats are naturally gluten free, they are often cross contaminated from other grains so make sure you buy oats that are labeled "gluten-free" if you need this.
You can mash the banana with a fork, whisk the dry ingredients and stir the rest in by hand if you don't have a hand mixer.
If needed, you can substitute pure maple syrup or agave instead of honey.