Heat the oven to 350°F and grease or line a muffin tin with liners.
In a large bowl, stir together the bananas, olive oil, milk, and maple syrup.
Sift in the flour, baking powder, baking soda, cinnamon, and salt. Gently fold ingredients together until combined. Add chocolate chips and walnuts.
Pour the batter into muffin cups until almost full, about ⅔ the way up the cup.
Place in the oven and bake for 15-20 minutes or until golden brown and a tester inserted in the middle of a muffin comes out mostly clean. Remove and let cool on a wire rack.
Notes
Add nuts - Add ½ cup of crushed walnuts or almonds for a light crunchy texture.
Substitute some almond flour - If nuts aren't an issue, substitute ¼ of the flour with almond flour for extra protein and added moisture.
Double the batch - You can easily make a double batch of muffins! Just multiply the quantities in the recipe card by 2, or check the toggle for "2x".
Make as regular-sized muffins - Bake these mini banana muffins in a regular-sized muffin tin. You will need to adjust the baking time if you bake larger muffins.
Use coconut sugar - For another natural sweetener option, swap coconut sugar for the maple sugar.