In a large bowl, combine flour, oats, baking powder, salt, and cinnamon.
In a smaller bowl, mash bananas together with applesauce, sugar, eggs, and vanilla. Add the wet ingredients to the dry and stir until combined. Stir in walnuts.
Spoon batter into a well-greased muffin tin and top with chopped walnuts and chocolate chunks if you'd like.
Bake the muffins for 20 minutes.
Recipe by Uproot Kitchen at https://uprootkitchen.com/2014/06/09/banana-walnut-muffins/