Banana Bars with Brown Butter Frosting are one of the best ways to use up overripe bananas. They are a mix between banana cake and banana blondies, topped with the most delicious frosting. These moist banana bars are easy to make and will be loved by the whole family.
Brown butter buttercream is one of my favorite frostings. If you’ve never had it, you’re in for a treat. It has a nutty toffee or caramel like flavor and goes SO well with many sweets and savory dishes too.
This banana bar recipe is perfect for any occasion:
- Casual weekend bake
- Birthday party
- Kids lunches (my kids love these and especially love the frosting)
- Holiday parties
Next time you need a quick way to use up those brown bananas, make these Banana Bars with Brown Butter Frosting. They’re definitely a great treat the whole family will love!
What is brown butter?
Brown butter is butter that has been heated on the stove top until it becomes brown with nutty, toffee or caramel like aroma and taste. It is basically liquid gold. It adds such a unique and wonderful flavor to sweet and savory dishes.
If you’ve never had brown butter then you definitely need to give it a shot! You’ll be wondering why you waited so long to try it!
How to make brown butter
Making brown butter is really easy. I know a lot of people are intimidated or scared to try it. There are really just a few simple steps:
- Melt your butter in a sauce pot over medium – low heat. Stir it occasionally to ensure even melting
- The butter will start sputtering and crackling. This is normal, it’s what you want. This is when you need to keep a close eye though
- Swirl the butter around every 20 seconds or so. You can also stir it with a whisk or wooden spoon
- The butter will start to brown slightly on the bottom of the pan. You know the butter is ready when it “quiets down”. The butter will stop sputtering and making noise and that’s when it’s perfect to take off. The butter should be a nice golden amber color
- Immediately pour the butter out of the pan into a heat proof container and set it aside until needed. Go ahead and use a rubber spatula to get all of the butter and the brown specks too. Now you have browned butter!
How to get bananas to ripen quickly
Want to make these Banana Bars with Brown Butter Frosting but don’t have any overripe bananas?! You always want to use overripe bananas in baking, they provide the best banana flavor.
Don’t worry, there are a few hacks you can use to go from yellow bananas to brown bananas. These tips are for ripening bananas to bake with, not to eat as a raw snack.
This is one of the best baking hacks. Now you don’t have to wait for days while you have a craving for the best banana bars. You can use your bananas no matter what stage they’re in!
Bake the bananas
Preheat the oven to 300°F then line a baking sheet with parchment paper. Place the bananas on the sheet then bake for 20-30 minutes. You’ll want the bananas to be very dark brown – black. Remove them from the oven, let them cool then peel and use them!
Microwave the bananas
Alternatively, you can microwave the bananas to speed up the ripening process. Microwave your bananas for 30 seconds and check for brownness. If they aren’t quite brown yet then continue to microwave in 15 second intervals until you’ve reached desired color.
I will say, I prefer the oven method over the microwave if you’re in a pinch and don’t have overripe bananas but either will work.
Can you freeze bananas?
Yes, absolutely! If you have leftover bananas that are overripe then you can freeze them. Just thaw out the frozen bananas prior to using them for baking. Here’s my favorite way to freeze them:
- Peel the banana then discard the skin
- Place the banana into a plastic re-sealable bag. I like to use 2 bags to help prevent freezer burn
- Put a date on the bag then freeze the bag of banana. Keep them frozen for up to 3 months
Ingredients needed for Banana Bars with Brown Butter Frosting
- Butter – I use unsalted butter so that I can control the salt level myself
- Brown Sugar – Generally I use dark brown sugar but either light or dark would be fine
- Eggs – Room temperature eggs are best for this recipe
- Bananas – Overripe bananas provide the best flavor when baking
- Vanilla Extract – Vanilla is a great base flavor when baking
- Rum Extract – I love rum and bananas so I added a little rum extract
- Kosher Salt – Salt brings out the flavor of all the ingredients in these banana bars
- All Purpose Flour – I have not tested this recipe with any other flours
- Baking Powder – For just a little rise in the banana bars
- Powdered Sugar – Sift your powdered sugar before adding it to the frosting
- Milk – I use whole milk but whatever you prefer is fine, including plant based milks
- Flaky Sea Salt (optional) – I always like a little flaky salt on top of my desserts
Equipment needed for Banana Bars
- Large Mixing Bowl – You’ll need a large mixing bowl to whisk the wet ingredients together
- Medium Mixing Bowl – I use a medium mixing bowl to whisk together the dry ingredients
- Whisk – A whisk for mixing the wet and dry ingredients together
- 8×8 Baking Pan – I use a metal 8×8 inch pan. If using a different size then the time would need to be altered. I’ve only used an 8×8 pan
- Parchment Paper – A good baking hack for bars, brownies and blondies is to spray the bottom of the pan with non-stick cooking spray then line it with parchment paper for easy removal of the bars
- Rubber Spatula – Use a rubber spatula to fold the flour mixture into the wet ingredients
Tips for the best Banana Bars with Brown Butter Frosting
- After making the brown butter frosting, beat it for a minute with a rubber spatula to get some of the air out before spreading it on the bars
- Make sure the banana bars are fully cooled before frosting them
- Use ripe bananas for this recipe. And by ripe I mean dark brown
- Don’t overmix the batter
- Room temperature ingredients will provide you with the best results
- My favorite way to jazz these banana bars up a little bit is to add chocolate chips, walnuts or pecans. Chocolate chip banana bars are always a hit
- The brown butter frosting recipe can be made up to 3 days ahead of time then stored in an airtight container in the fridge. Let it come to room temp before frosting the banana bars
- You can make the brown butter the night before to save time. Let it sit out on the counter all night, covered. You’ll need it to be room temp to cool before using it anyways
How to store Banana Bars with Brown Butter Frosting
Banana Bars with Brown Butter frosting can be stored multiple different ways, depending on how quickly you plan to eat them. Here are the 3 ways that I use:
- Store them on the counter in an airtight container or tightly double wrapped with plastic wrap. The banana bars will last up to 3 days on the counter
- Store them in the fridge in an airtight container or tightly double wrapped with plastic wrap. Storing them in the fridge will give them a little extra shelf life. You can keep them for up to 6 days this way. Although they are still delicious when chilled, I would recommend bringing the banana bars to room temp on the counter before eating
- Store them in the freezer. To store the banana bars in the freezer, make sure they are fully cooled first. You can store them in the freezer with or without the frosting. Wrap them tightly in plastic wrap 2-3 times then in aluminum foil 1 time. They will last in the freezer for up to 2 months
For all of these storage methods you can either store the entire pan or you can cut slices and store individual pieces.
How to make Banana Bars with Brown Butter Frosting
Preheat the oven to 350°F then spray the 8×8 inch pan with non-stick cooking spray, line it with parchment paper then spray the parchment paper with non-stick spray as well. Melt the butter and our it into a large bowl.
Add the brown sugar and whisk until smooth. Mix in the room temperature eggs one at a time. Stir in the vanilla and rum extracts. Add the mashed bananas, stir them in then set aside.
In a separate bowl, whisk together the flour, salt and baking powder. Add the dry ingredients into the wet ingredients and fold just until combined. A streak or two of flour is okay. Do not overmix the batter.
Pour batter into the prepared pan then bake for 30 minutes. Insert a toothpick and when it comes our clean or with just a few crumbs the banana bars are done. Remove them from the oven and let them cool on a wire rack.
While the banana bars are cooling, make the brown butter frosting. Place the cooled brown butter (directions in “how to make brown butter” section above) and sifted powdered sugar into the bowl of a stand mixer fitted with the paddle attachment. Alternatively, you can use a medium bowl with an electric mixer if you don’t have a stand mixer.
Mix on low speed until combined then turn it up to medium for 1 minute. Turn the mixer off then add the vanilla, milk and salt. Mix on low just until combined then turn up to medium – high for 4 minutes. The frosting should be light and airy.
Once the banana bars are completely cooled then frost them with the brown butter frosting and serve. If you’d like you can garnish the top of the banana bars with sliced bananas but only if you’re serving them immediately.
The sliced banana can get brown and a little slimy once it sits too long.
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Try my Chocolate Espresso Banana Bread!
Banana Bars with Brown Butter Frosting
- 1 large and medium mixing bowls
- 1 8×8 inch metal baking pans
- 1 whisk
- 1 rubber spatula
- 1 parchment paper
- 1 cup unsalted butter melted then cooled slightly
- 1¾ cup brown sugar
- 2 eggs room temp
- 2 tsp vanilla extract
- 2 tsp rum extract
- 1 cup mashed banana overripe
- 2 cups all purpose flour
- ½ tsp kosher salt
- ½ tsp baking powder
Brown Butter Frosting
- 1 cup brown butter cooled
- 2 cups powdered sugar sifted
- ½ tsp vanilla extract
- 1 tbsp whole milk
- ¼ tsp kosher salt
- ¼ tsp flaky sea salt on top of the frosted banana bars
- 1 banana sliced, placed on top of frosted banana bars
Mixing the Wet Ingredients
- Preheat the oven to 350°F then spray an 8×8 inch pan with non stick cooking spray, line it with parchment paper and spray the parchment paper with non stick spray
- Whisk the melted butter and brown sugar together until smooth in a large bowl
- Stir in the eggs one at a time
- Add the vanilla and rum extracts then stir in the mashed banana and set aside
Mixing the Dry Ingredients
- Whisk the flour, salt and baking powder together in a medium bowl
- Fold the dry ingredients into the wet ingredients just until combined. Do not over mix. A few streaks of flour are fine
- Pour the batter into prepared pan and spread evenly. Bake for 30 minutes or until a toothpick comes out clean or with only a few crumbs
- Allow the banana bars to cool completely on a wire rack
Making the Brown Butter Frosting
- While the banana bars are cooking, add the cooled brown butter and sifted powdered sugar into the bowl of a stand mixer fitted with the paddle attachment
- Mix on low until combined then turn up to medium for 1 minute
- Add the vanilla, milk and salt. Mix on low until combined then mix on medium – high for 4 minutes until light and fluffy
- Once banana bars are cooled then spread the frosting over the top and serve
- Top with flaky sea salt or sliced banana if you like