Heat oven to 350℉
Line 2 muffin tins with paper liners, or spray with baking spray. Set aside.
In a medium bowl, mash bananas, buttermilk, and vanilla together. Set aside.
In a large bowl, whisk together flour, granulated sugar, brown sugar, baking powder, baking soda, and salt.
In a small bowl, whisk together eggs, egg yolk, and coconut oil.
Pour over dry ingredients.
Mix together.
Add bananas, coconut, and chocolate chips.
Stir only to blend.
Use a cookie scoop or Tablespoon to fill muffin cups ⅔ full.
Sprinkle tops with mini chocolate chips and coconut flakes.
Bake for 25 minutes, or until done.