Directions

1. Position an oven rack in the center of the oven and preheat to 400 degrees F. Line a 12-cup muffin pan with paper liners.  Whisk together the whole-wheat flour, all-purpose flour, baking powder, cinnamon, baking soda and salt in a medium bowl.
2. Whisk together the coconut oil, brown sugar, maple syrup, vanilla and egg whites in a separate medium bowl until well combined. Stir in the mashed banana. Add the dry ingredients to the wet and stir until combined. Stir in the chopped walnuts if using.  
3. Fill the lined muffin cups about three-quarters of the way with the batter (a generous 1/4 cup in each; see Cook's Note). Bake on the center rack until a cake tester or toothpick inserted in the center of a muffin comes out clean, 20 to 25 minutes. Let cool 10 minutes, then remove the muffins to a wire rack to cool completely.