Preheat your oven to 350°F (175°C) and grease a muffin tin or line with muffin liners.
In a large mixing bowl, mash the ripe bananas until smooth.
Add the melted coconut oil, maple syrup, and vanilla extract to the mashed bananas and mix well.
Sprinkle the baking soda, salt, and ground cinnamon over the mixture and stir to combine.
Gently fold in the whole wheat flour until just combined. Do not overmix.
Add the almond milk and stir until the batter is smooth. If using, fold in the chopped walnuts.
Divide the batter evenly among the muffin cups, filling each about ¾ full.
Bake for 20-25 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
Allow the muffins to cool in the tin for 5 minutes, then transfer to a wire rack to cool completely.