Step 1

Preheat oven to 350°F. Spray a 9x13-inch baking pan with non-stick cooking spray. Set aside.

Step 2

In a medium bowl, whisk together the flour, baking powder, baking soda, cinnamon and salt. Set aside.

Step 3

In a large bowl, with an electric mixer, cream together the butter, brown sugar and granulated sugar, until combined and fluffy.

Step 4

Add the eggs, mashed banana, buttermilk and vanilla and mix well.

Step 5

Gradually add the flour mixture into the banana mixture, mixing until well combined.

Step 6

Stir in the chopped walnuts.

Step 7

Pour the batter into the prepared baking pan and bake for 20 minutes, until the edges are golden, and a toothpick inserted in the center comes out with just a few crumbs.

Step 8

In a small saucepan, over medium heat, melt the butter and cook until it is a golden brown, and has a nutty aroma. Immediately, remove from the heat and stir in the powdered sugar, half and half cream and vanilla.

Step 9

Using a silicone spatula spread the frosting over the warm banana brownies.