Preheat oven to 350°F (180°C) and prepare a muffin mold with cupcake liners. Make sure you grease the liners to prevent muffins from sticking.
In a large mixing bowl mash three ripe bananas with a fork until completely smooth. Stir nut butter, eggs and vanilla extract into the banana mixture.
Add coconut sugar and salt. Stir the wet mixture with a whisk or fork for around two minutes, or until all is well combined.
Stir in oat flour (or preferred flour), cocoa powder and baking powder. Mix just until the batter reaches a smooth texture and is free of lumps, but do not overmix. Then fold through chocolate chips.
Fill ⅔ of each muffin liner with the batter, sprinkle with more chocolate chips and bake in hot oven for 20 to 25 minutes. Make sure you do not overbake the muffins; they are ready when a toothpick inserted into the center comes out clean.
Remove chocolate banana muffins from the oven and let cool over a baking rack for about 15 minutes.