Preheat your oven to 350º
Peel and mash the bananas in a medium-sized mixing bowl. The bananas should be a paste-like consistency with few lumps. I find that using a potato masher makes this very easy
Add the maple syrup, 1/4 cup of coconut oil, gluten-free flour, baking powder and vanilla. Stir to combine. The batter should be similar in consistency to thick pancake batter
Stir in the chocolate chips and, if desired, the chopped walnuts
Lightly grease the muffin tin with coconut oil
Fill each of the muffin compartments 2/3rds full with the muffin batter
Bake for 18 minutes. Check for doneness by inserting a toothpick into a muffin. The toothpick should come out cleanly.