
This banana bread brownie recipe combines two beloved treats into one irresistible dessert. The soft, cake-like texture studded with ripe bananas gets elevated with a decadent brown butter frosting that takes these bars to the next level. Perfect for potlucks, family gatherings, or whenever you have overripe bananas begging to be transformed.
I first made these brownies for a neighborhood bake sale where they sold out faster than anything else on the table. Now whenever I spot bananas turning brown on my counter, my family starts dropping hints about making these bars.
Ingredients
- Sugar: Provides the perfect sweetness to balance the banana flavor while creating that classic brownie texture
- Sour cream: Adds incredible moisture and a subtle tanginess that enhances the overall flavor profile
- Butter: Creates richness in both the brownies and the magical brown butter frosting
- Eggs: Work as a binding agent while adding structure to these cake-like bars
- Ripe bananas: Are the star ingredient; look for ones with plenty of brown spots for maximum flavor
- Vanilla extract: Enhances both the banana and chocolate notes
- All purpose flour: Gives structure while keeping the texture tender
- Baking soda: Helps these bars rise perfectly while maintaining moistness
- Salt: Balances the sweetness and enhances all other flavors
- Walnuts: Add a wonderful textural contrast and nutty flavor
- Powdered sugar: Creates that smooth luxurious frosting
- Milk: Thins the frosting to the perfect consistency for spreading
Step-by-Step Instructions
- Prepare the Batter:
- Cream together sugar, sour cream, butter, and eggs until light and fluffy. This creates the foundation for a tender texture. Take your time here—at least 3 minutes of beating incorporates air that helps the brownies rise properly. Fold in those mashed bananas and vanilla extract just until combined.
- Mix Dry Ingredients:
- Add flour, baking soda, and salt to your wet ingredients and mix for exactly one minute. Overmixing will develop too much gluten and create tough brownies. You want the batter to be just combined with no visible flour pockets. Gently fold in the walnuts last to preserve their texture.
- Bake to Perfection:
- Spread the batter carefully into your prepared jelly roll pan, ensuring it reaches all corners evenly. This promotes uniform baking. Watch the edges carefully during the last few minutes—they should be turning golden brown while the center remains slightly soft. A toothpick inserted should come out with a few moist crumbs.
- Create Brown Butter Frosting:
- Heat butter in a saucepan until it turns a beautiful amber color, swirling occasionally to prevent burning. The milk solids will begin to brown and release a nutty aroma that signals perfection. Remove from heat immediately once the color changes to prevent burning. Whisk in powdered sugar, vanilla, and milk until velvety smooth.
- Apply Frosting While Warm:
- Spread the brown butter frosting over the bars while they are still warm. The residual heat helps the frosting spread more easily and creates a slight melding of flavors between the frosting and bars. Work quickly as the frosting will begin to set as it cools.

The first time I browned butter for this recipe, I nearly threw it away thinking I had ruined it. That nutty aroma and golden color seemed like a mistake until I tasted the finished product. Now browning butter is my secret weapon for elevating many desserts, but none showcase it better than these banana bread brownies.
Storage and Make-Ahead Tips
These brownies actually taste better the day after baking as the flavors have time to meld together. Store them in an airtight container at room temperature for up to 4 days. For longer storage, refrigerate for up to a week—though they rarely last that long in my house. The texture remains impressively moist thanks to the bananas and sour cream.
Banana Selection Matters
The ripeness of your bananas dramatically affects the flavor of these brownies. For the best results, use bananas that are heavily speckled with dark spots or even completely black. These overripe bananas have developed more sugar content and stronger banana flavor. If your bananas are not ripe enough, you can quickly ripen them by placing them in a paper bag with an apple for 24 hours.
Serving Suggestions
While these brownies are perfection on their own, try warming a square slightly and topping it with a scoop of vanilla ice cream for a restaurant-worthy dessert. For brunch, serve them alongside fresh fruit and coffee. They also make wonderful gifts packed in decorative tins or boxes with parchment paper between layers to prevent sticking.
The Magic of Brown Butter
Brown butter is simply regular butter that has been cooked until the milk solids caramelize, creating a nutty, complex flavor that elevates any dessert. The key is patience—watch the butter carefully as it can go from perfectly browned to burnt in seconds. The color should be amber, like maple syrup, and the aroma will become intensely nutty when ready.
Frequently Asked Questions
- → How do I get the perfect brownie texture?
Ensure you measure ingredients precisely, don’t over-mix the batter, and bake within the given time for soft, chewy results.
- → Can I make these brownies without walnuts?
Yes, you can omit walnuts if you prefer a nut-free version. The brownies will still be deliciously soft and flavorful.
- → What’s the key to the brown butter frosting?
Heat the butter until golden brown for a nutty, rich flavor. Be careful not to burn it, and whisk in the remaining frosting ingredients while the bars are warm.
- → Can I use overripe bananas for this?
Yes, overripe bananas work best as they bring natural sweetness and moisture to the brownies.
- → How should I store these brownies?
Store them in an airtight container at room temperature for up to 3 days or refrigerate for extended freshness.