Banana Bread Bars with Brown Butter Frosting

Preheat oven to 350 degrees F (175 degrees C). Grease and flour a 15x10-inch jelly roll pan.

Beat white sugar sour cream 1/2 cup softened butter and eggs in a bowl with an electric mixer until creamy. Beat in bananas and 2 teaspoons vanilla extract. Add flour baking soda and salt; mix for 1 minute. Stir walnuts into batter until evenly incorporated. Spread batter in prepared pan.

Bake in the preheated oven until golden about 27 minutes. Cool.

Melt 1/2 cup butter in a large saucepan over medium heat until bubbling and golden brown 3 to 5 minutes. Remove from heat.

Whisk confectioners' sugar milk and vanilla extract into melted butter until a smooth frosting consistency is reached. Spread frosting over cooled banana bars.