Set your oven to 375°F (190°C). Grease a 13 x 9 inch baking pan thoroughly to ensure the brownies don’t stick.

In a large bowl, beat together the sugar, sour cream, softened butter, and eggs until the mixture is smooth and creamy. This step is key for a soft and moist texture!

Fold in the mashed bananas and vanilla extract. These two ingredients add that unmistakable banana bread flavor we all know and love.

Gradually mix in the flour, baking soda, and salt. Blend for about a minute to ensure all the ingredients are evenly combined.

Stir in the chopped walnuts, which add a delightful crunch to each bite. If you’re not a fan of nuts, feel free to skip this step.

Spread the batter evenly in your prepared pan. Bake for approximately 25 minutes or until the top turns golden brown and a toothpick inserted into the center comes out clean.

While the brownies are cooling, heat the butter in a large saucepan over medium heat until it reaches a medium brown color. Carefully watch it to avoid burning.

Remove from heat and gradually whisk in the powdered sugar, adding the milk little by little until the frosting reaches a smooth, spreadable consistency. Stir in the vanilla extract for an extra hint of sweetness.

Pour the frosting over the warm (but not hot) brownies and spread evenly. Allow the banana bread brownies to cool completely before cutting into squares.