Preheat Oven:
Preheat your oven to 375°F (190°C). Grease and flour a 15×10-inch jelly roll pan to prepare for the batter.
Prepare the Batter:
In a large mixing bowl, beat together the sugar, sour cream, butter, and eggs until the mixture becomes creamy. Blend in the mashed bananas and vanilla extract.
Combine Dry Ingredients:
Add the flour, baking soda, and salt to the wet mixture. Blend for about 1 minute until everything is well combined. Stir in the chopped walnuts.
Bake the Bars:
Spread the batter evenly into the prepared pan. Bake for 20 to 25 minutes or until the bars are golden brown and a toothpick inserted into the center comes out clean.
Make the Frosting:
While the bars are baking, prepare the brown butter frosting. In a large saucepan over medium heat, melt the butter and let it cook until it turns a delicate brown color. Remove from heat immediately.
Combine Frosting Ingredients:
Add the powdered sugar, vanilla extract, and milk to the browned butter. Whisk together until the mixture is smooth and has a consistency thicker than a glaze but thinner than traditional frosting.
Frost the Bars:
Once the bars are baked, remove them from the oven and let them cool slightly. Spread the brown butter frosting over the warm bars using a spatula. The frosting will spread more easily while the bars are still warm.
Serve:
Allow the bars to cool completely before cutting into squares and serving.
Enjoy these Banana Nut Bars with their delicious brown butter frosting as a delightful dessert or snack!
