Step 1: Preheat the Oven
Preheat your oven to 350°F (175°C).
Grease a 9-by-13-inch baking dish with butter or nonstick cooking spray. You can also line the dish with parchment paper, leaving a little overhang to make removing the brownies easier.
Step 2: Mash the Bananas
Peel the ripe bananas and place them in a large mixing bowl.
Mash them with a fork until mostly smooth. A few small lumps are perfectly fine and will add texture to the finished brownies.
For the best flavor, use bananas with plenty of brown spots on their skins. These are generally sweeter and easier to mash than firm, underripe bananas.
Step 3: Add the Wet Ingredients
Add the eggs, sour cream, and vanilla extract to the mashed bananas.
Whisk everything together until the mixture is smooth and well combined.
The sour cream helps create a moist texture, while the eggs provide structure and help the brownies hold together after baking.
Step 4: Combine the Dry Ingredients
In a separate bowl, whisk together the all-purpose flour, granulated sugar, baking soda, and salt.
Mix thoroughly to distribute the baking soda evenly throughout the flour.
Step 5: Make the Batter
Gradually add the dry ingredients to the banana mixture.
Stir gently with a spatula or wooden spoon until the flour is incorporated and no large dry patches remain.
Avoid overmixing, as excessive stirring can develop the gluten in the flour and make the brownies tougher.
The batter should be thick but easy to spread.
Step 6: Transfer to the Baking Dish
Pour the batter into the prepared baking dish.
Use a spatula to spread it evenly into the corners so the brownies bake at a consistent thickness.
Gently tap the dish on the countertop to release any large air bubbles.
Step 7: Bake the Banana Bread Brownies
Place the dish in the preheated oven and bake for approximately 25–30 minutes.
The baking time may vary depending on your oven and the depth of your baking dish.
Check the center with a toothpick. It should come out clean or with a few moist crumbs, but without wet batter.
If the center is still underbaked, continue baking for another 3–5 minutes and check again.
Remove the dish from the oven and allow the brownies to cool completely before adding the frosting.
Step 8: Brown the Butter
Place the unsalted butter in a light-colored saucepan over medium heat.
Allow it to melt, stirring occasionally. The butter will begin to foam and then develop golden-brown specks at the bottom of the pan.
Continue cooking carefully until the butter smells nutty and has a golden amber color.
Remove the pan from the heat immediately to prevent the butter from burning.
Let it cool for several minutes before preparing the frosting.
Step 9: Prepare the Frosting
Transfer the browned butter to a mixing bowl.
Add the powdered sugar and vanilla extract. Mix on low speed until the ingredients begin to combine.
Gradually add the milk, one tablespoon at a time, until the frosting reaches a smooth, spreadable consistency.
Add a small pinch of salt if desired to balance the sweetness.
If the frosting is too thick, add a little more milk. If it is too thin, mix in additional powdered sugar.
Step 10: Frost the Brownies
Make sure the banana brownies are completely cool before frosting them.
Spread the brown butter frosting evenly over the surface using a spatula or the back of a spoon.
For a decorative finish, create gentle swirls across the frosting.
Allow the frosting to set for a few minutes before cutting the brownies into squares.
Step 11: Slice and Serve
Cut the brownies into squares and carefully lift them from the baking dish.
Serve them at room temperature with coffee, tea, or a cold glass of milk.
Each square offers a delicious combination of sweet banana flavor, a moist crumb, and rich frosting with a subtle nutty aroma.
Tips for Perfect Banana Bread Brownies
Use very ripe bananas: Bananas with brown spots provide the sweetest flavor and help keep the brownies moist.
Measure the flour carefully: Too much flour can make the brownies dry. Spoon flour into your measuring cup and level it off rather than packing it down.
Do not overmix the batter: Stir only until the ingredients are combined to help maintain a soft texture.
Watch the butter closely: Brown butter can burn quickly. Remove it from the heat as soon as the milk solids turn golden brown and smell nutty.
Cool before frosting: Frosting warm brownies can cause the buttercream to melt and slide off.
Adjust the frosting consistency: Add milk gradually so the frosting remains thick enough to spread without running.
Delicious Variations
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