Banana Bread Brownies with Brown Butter Frosting

These Banana Bread Brownies combine the soft, moist texture of homemade banana bread with the easy-to-serve shape of classic brownies. Ripe bananas, sour cream, and vanilla keep every bite tender, while a rich brown butter frosting adds a sweet, nutty finish. They are an easy dessert for family gatherings, potlucks, holidays, or simply using up ripe bananas.

Ingredients

For the Banana Bread Brownies

• ½ cup unsalted butter, softened
• 1 cup granulated sugar
• 2 large eggs
• 1 cup sour cream
• 1 teaspoon vanilla extract
• 2 cups all-purpose flour
• 1 teaspoon baking soda
• ¼ teaspoon salt
• 1 cup mashed ripe bananas, about 2–3 bananas

For the Brown Butter Frosting

• ½ cup unsalted butter
• 4 cups powdered sugar
• 1½ teaspoons vanilla extract
• 3 tablespoons milk, plus more if needed

Instructions

1. Preheat the oven to 375°F (190°C). Lightly grease and flour a 9×13-inch baking dish, making sure the bottom and corners are evenly coated.
2. Place the softened butter and granulated sugar in a large mixing bowl. Beat together until the mixture becomes smooth, creamy, and slightly fluffy.
3. Add the eggs one at a time, mixing well after each addition. Stir in the sour cream and vanilla extract until everything is evenly combined.
4. In a separate bowl, whisk together the all-purpose flour, baking soda, and salt.
5. Gradually add the dry ingredients to the butter mixture. Stir gently just until combined. Avoid overmixing, as this can make the brownies less tender.
6. Fold the mashed ripe bananas into the batter until evenly distributed.
7. Spread the batter evenly into the prepared 9×13-inch baking dish. Smooth the surface with a spatula.
8. Bake for 20–25 minutes, or until the top is lightly golden and a toothpick inserted into the center comes out clean or with only a few moist crumbs.
9. Remove the pan from the oven and place it on a wire rack. Allow the banana brownies to cool completely before frosting.

How to Make the Brown Butter Frosting

1. Place the butter in a medium saucepan over medium heat. Allow it to melt completely.
2. Continue cooking the butter while stirring or swirling the pan occasionally. It will foam and gradually develop golden-brown specks with a nutty aroma.
3. As soon as the butter reaches a delicate golden-brown color, remove it from the heat to prevent burning.
4. Transfer the browned butter to a mixing bowl. Add the powdered sugar, vanilla extract, and milk.
5. Beat until the frosting becomes smooth and creamy. If it is too thick, add a little additional milk, one teaspoon at a time.
6. Spread the frosting evenly over the completely cooled banana bread brownies.
7. Allow the frosting to set slightly before slicing the dessert into squares and serving.

Tips for the Best Banana Bread Brownies

Very ripe bananas work best for this recipe. Bananas with plenty of brown spots are naturally sweeter, softer, and easier to mash, giving the brownies a stronger banana flavor.

Be careful not to overbake the brownies. Start checking them around the 20-minute mark. The center should be cooked through while remaining soft and moist.

The brownies should also be completely cool before adding the frosting. Spreading frosting over a hot cake can cause it to melt and become too thin.

Optional Add-Ins

For additional texture, you can fold chopped walnuts or pecans into the banana batter. Chocolate chips are another delicious addition if you prefer a banana-and-chocolate combination.

Serving Suggestions

Serve these banana bread brownies at room temperature with coffee, tea, or a cold glass of milk. For dessert, a slightly warmed square can also be served with vanilla ice cream.

Storage

Keep the brownies covered in an airtight container at room temperature for up to 2 days. For longer storage, refrigerate them for up to 5 days. Allow refrigerated brownies to sit at room temperature briefly before serving for a softer texture.

Frequently Asked Questions

How ripe should the bananas be?

Use very ripe bananas with yellow skins covered in brown spots. The softer and riper the bananas are, the sweeter and more pronounced their flavor will be.

Can I make these without the frosting?

Yes. The banana brownies are moist enough to serve on their own. You can also simply dust them with powdered sugar for a lighter finish.

Can I add nuts?

Yes. Chopped walnuts or pecans work especially well. Fold about ½ cup into the batter before transferring it to the baking dish.

Why is it called brown butter frosting?

The butter is gently cooked until the milk solids become golden brown. This creates a deeper, slightly nutty flavor that pairs especially well with banana desserts.