Preheat the oven to 180C/350F. Line a 12-count muffin tin with muffin liners and lightly spray with coconut oil. Set aside.
In a large mixing bowl, add your dry ingredients and mix well. In a high speed blender, add your bananas, egg, maple syrup, and vanilla extract, and blend until smooth.
Add the wet ingredients into the dry ingredients. Fold through the chocolate chips and walnuts. Distribute the batter into the muffin liners. Bake the muffins for 18-20 minutes, or until golden on top and a skewer comes out clean.
Let the muffins cool in the pan for 10 minutes, before transferring to a wire rack to cool completely.
TO STORE: If you intend to enjoy the muffins within 3 days, they can be stored at room temperature in a sealed container. If you'd like them to keep longer, store them in the refrigerator, covered, for up to 1 week.TO FREEZE: Place the muffins in a ziplock bag and store them in the freezer for up to 6 months. Recipe loosely adapted from here.