Preheat oven to 350°F. Generously spray 8 cavities with cooking spray. Do not use muffin liners; these muffins stick to the liners.
Remove the banana peel and mash well with a fork. Measure the banana after it has been thoroughly mashed.
In a large bowl, mix together the mashed banana, peanut butter (do not warm up), honey, vanilla extract, brown sugar, and egg. Mix until thoroughly combined.
To make the oat flour, pulse oats in a blender or food processor until they have a flour-like consistency. Make sure to measure the oat flour after blending and not before.
To the bowl with the wet ingredients, add the salt, baking soda, baking powder, oat flour, old-fashioned oats, and dark chocolate chips. Mix until thoroughly combined.
Using a cookie scoop, scoop 2 full scoops of the dough into each muffin cavity, filling 8 cavities. Bake at 350℉ for 15–18 minutes or until lightly browned along the edges and no longer gooey or wet-looking on top. Watch carefully so they don’t burn and end up less flavorful and crumbly.
Let cool for 3–5 minutes in the muffin pan, then use the tines of a fork to gently coax the muffins out of the tin. Transfer to a wire cooling rack to allow the muffins to finish cooling.
Video
Notes
Note 1: If you like your muffins sweeter, increase brown sugar by 1–2 tablespoons. Depending on your preference, start with 4 tablespoons and go up to 6.Note 2: Make sure oats are certified gluten-free to have a gluten-free muffin.Storage: Store leftover muffins in an airtight container at room temperature for up to 2 days, or refrigerate for up to a week. Freeze for longer storage.