Preheat oven to 350 degrees F & line a muffin pan with muffin liners
In a mixing bowl, mash bananas thoroughly with a fork. Add in milk and coconut oil and mix until smooth. Finally, mix in oat flour and baking powder.
Add in chocolate chips and walnuts, leaving a few to add on top (if desired). Fill 10-12 muffin slots almost to the top and sprinkle with additional chocolate chips and walnuts.
Bake for 20-22 minutes, or until toothpick comes out smooth.