Preheat the oven to 350 degrees F. Spray a 9x13 baking dish with cooking spray.

In a large mixing bowl, stir together the flour, baking soda, cinnamon and salt until well combined. Set aside.

With a hand held electric mixer, cream together the butter and sugar until smooth and fluffy.

Mix in the eggs, mashed bananas and milk until combined.

Stir the dry ingredients with the wet ingredients.

Hand mix in the chopped walnuts.

Pour the batter into the prepared pan. Bake for 20-25 or until a toothpick inserted into the center comes out clean.

While the bars are cooling, make the frosting.

Mix together the butter and cream cheese on medium-high speed for 3 minutes with a hand held mixer or stand up mixer. Mix in the vanilla extract.

Reduce the mixer speed to low and gradually add the powdered sugar until combined.

Increase the mixer speed to medium-high and beat (for 3-4 minutes) until the frosting mixture is fluffy.

Once the bars are completely cool, spread the frosting on top using an offset spatula.

Then the bars are ready to slice, serve and enjoy!