Preheat the oven to 350°F. Line the muffin tin or lightly mist the tin with cooking spray. Set aside.
Mix dry ingredients: In a large bowl, combine the rolled oats, whole wheat flour, almond meal, cocoa powder, baking soda, and salt.
Mix wet ingredients: In a medium bowl, add the bananas. Mash the banana with the back of a fork or with a potato masher until thoroughly broken down. Add the eggs, maple syrup, peanut butter, almond milk, olive oil, and vanilla extract. Whisk well until smooth.
Make a small well in the dry ingredients and pour the wet ingredients into the well. Mix the batter together, until juts incorporated. Be careful not to over-mix. There can be a few streaks of flour and some bumps in the batter. Fold in the walnuts and chocolate chips.
Spoon a generous amount of batter into each muffin tin. You'll want to fill it until nearly full. These muffins are a little more dense and make small domes, so it's okay to fill the tins completely. This recipe yields about 12 muffins.
Cook the muffins for 22 to 26 minutes, or until a toothpick comes out clean when inserted into the middle of the muffin. Remove the muffins from the oven and place on a cooling rack. Allow the muffins to cool completely inside of the muffin tin before removing. Enjoy!