Preheat the over to 375 degrees and spray a muffin tin with cooking spray, set aside.
In a large bowl, combine the flour, baking soda and salt. Set aside.
In a small bowl, mash 2 of the bananas with a fork, set aside.
With an electric mixer (use the wire whisk on a stand mixer), whip the remaining bananas and sugar together for 2 minutes. Add the melted butter, eggs and vanilla and beat well. Mix in the dry ingredients just until incorporated, do not overmix. Fold the mashed bananas into the mixture. Using an ice cream scooper or spoon, fill the muffin cups halfway. Tap pan on the counter to remove any air bubbles.
Bake for 18-20 minutes, until a toothpick stuck in the center comes out clean. Let cool for 5 minutes in the pan before removing to a cooling rack.
While the muffins are cooling prepare the glaze.
Combine confectioners sugar, milk and maple syrup in a small bowl. Mix thoroughly. If the glaze is too thick, add more milk.
Drizzle the glaze over cooled muffins, then sprinkle with toasted walnuts. Enjoy!