Preheat the oven to 350°F and grease an 8x4 or 9x5-inch loaf pan. If desired, line the bottom and two long sides with a sheet of parchment paper.

In a large bowl, whisk together the mashed banana, maple syrup, coconut oil, eggs, and vanilla.

In a medium bowl, whisk together the all-purpose and whole wheat flours, baking soda, cinnamon, salt, and nutmeg.

Add the dry ingredients to the wet ingredients and stir until just combined. Don’t overmix. Fold in the walnuts.

Pour the batter into the prepared pan and sprinkle the oats evenly on top.

Bake for 50 to 65 minutes, or until the top springs back to the touch. A toothpick inserted should come out with just a few moist crumbs attached. I like to check the loaf after 45 minutes. If the top is golden brown, I cover it with foil for the remaining bake time to prevent further browning.