Preheat your oven to 350°F (175°C).
Grease a 9x13-inch baking pan with cooking spray or butter.
In a medium bowl, whisk together the flour, baking soda, baking powder, salt, and ground cinnamon. Set aside.
In a large bowl, mash the ripe bananas until smooth. Add the sugars, applesauce, sour cream, eggs, and vanilla extract. Mix until well combined.
Gradually add the dry ingredients to the wet ingredients. Mix until just combined.
Gently fold in the chocolate chips and walnuts.
Pour the batter into the prepared pan. Sprinkle the remaining walnuts on top.
Bake for about 45-50 minutes, or until a toothpick comes out clean.
Let it cool for 10 minutes, then transfer to a cooling rack. Prepare the glaze by whisking together the powdered sugar, vanilla extract, and milk until smooth. Drizzle over the cooled cake.
