Brown Butter Banana Cake with Chocolate Fudge Frosting

I’d like to introduce you to the brown butter banana cake, your new BFF (or should I say, BBBCwCFF?) It’s surprisingly light for a banana cake, with the perfect balance of sweetness and ripe banana flavor that’s enhanced by toasty nuttiness of brown butter. Best of all, both the cake and frosting can be mixed by hand, no electric mixer needed.

The fudge frosting is deeply and intensely chocolate—made with both melted chocolate and cocoa powder—with a silky smooth texture and shiny finish that stays soft even after being refrigerated. It’s the perfect fudgy compliment to the moist and tender banana cake, without the overpowering sweetness of other frostings (no powdered sugar in sight!)

When it comes to developing recipes, which comes first, the cake or the frosting? Normally, for me, it’s the cake, but not here. No, this recipe started from the top—luscious swirls of deeply chocolate fudge frosting—and the cake soon followed.

Would you believe that this fudge frosting was a complete accident? I found myself with a few random bowls of ganache/fudge left from my candied orange fudge swirl ice cream recipe (getting a fudge swirl that stayed soft and chewy even when frozen solid took a few tries to get right).

Not wanting to waste the remnants, I combined the bowls of ganachey fudge and fudgey ganache, added a splash of cream, and whipped it with an electric mixer to smooth it all out. The result made a surprisingly delicious whipped fudge frosting, which I then slathered on top of a thrown-together-because-those-three-overripe-bananas-need-to-be-used-stat banana cake to bring to ceramics class, which my classmates promptly devoured.

But despite the accidental awesomeness that was the first test cake, I somehow found myself sitting on this recipe for upwards of a year. Why? I can’t quite explain it. At first it was just about not wanting to post two square-ish bakes in a row, or posting too many cake recipes back to back, but when I finally revisited it, enough time had passed that the accidental frosting didn’t quite pass my exacting standards. It was close, but I knew I could make it better.

I wanted a shinier appearance, for one (whipped ganaches and the like often take on a matte appearance which I don’t love) and I felt that a more intense chocolate flavor would better compliment the delicate banana cake. So I ultimately nixed the whip and went for a dense and shiny fudge, with more dark chocolate than the original to ensure it set just firmly enough to hold its shape while still remaining soft enough to easily yield to a fork, even after refrigerating.

The presence of the other fudge sauce ingredients—butter, granulated sugar, and glucose syrup—makes this frosting different from a straight ganache, with a luscious, smooth texture that doesn’t fully harden in the fridge (which is one of my main qualms with ganache and buttercream frostings). And using both cocoa powder AND melted dark chocolate results in a deeply rich chocolate flavor that you simply can’t achieve with chocolate alone.

Cake it to the limit.

But enough about the frosting, let’s talk about the cake.

Because while I made upwards of 7 different versions of the frosting, the cake has been aces from the get-go, which is a rarity for me and my (ahem) high standards.

Unlike banana bread, which can have a dense and almost overly moist, claggy texture, this banana cake is light and elegant, with a tender crumb and a perfect amount of sweetness.

But the brown butter is what makes it truly sing. It’s not an obvious flavor, but if you compared it to a version made with regular melted butter you’d certainly notice the difference. The nuttiness of the brown butter lifts up the banana flavor, without any actual nuts (which would mar the perfectly tender texture and crumb of this cake, in my opinion).

Life is butter dream.

Brown butter is made by melting butter and cooking it until the milk solids separate and settle to the bottom of the pan and caramelize to a lovely rich golden brown color.

This browning (the Maillard reaction in action) gives the butter a deep, nutty, and complex flavor with notes of toffee, pecan, toasted brioche, and caramel (all of which are—you guessed it—complimentary flavors of banana).

Could you skip the brown butter step? Sure. You’d still end up with a lovely banana cake if you used plain melted butter. But I think it’d be missing that little something extra, that depth and complexity of flavor that only brown butter can provide. It’s worth the extra 5 minutes, trust me.

How to make it:

The cake itself is made with a similar method to banana bread, though the result is much lighter and elegant. Because it’s made using melted brown butter and not solid butter, the batter can be mixed by hand, no electric mixer needed (same for the frosting too!)

While the brown butter does add a few minutes to the prep time, the result is a subtle nuttiness and toasted flavor that compliments the banana beautifully, adding to the refined flavor of the banana cake.

Melt European-style salted butter in a saucepan (ideally light colored) set over medium heat.Let simmer until the solids separate out and turn golden brown.Pour hot brown butter into a heat-proof mixing bowl with granulated sugar; stir to combine.Let butter-sugar mixture cool slightly, then add eggs, whisking until smooth.Whisk in eggs until batter is smooth.Mash banana (I like to use a mini potato masher). 3 large bananas should yield approximately 1 cup.Mix in mashed banana.Add half of dry ingredients (flour, baking soda/powder, and salt) and mix until almost fully incorporated.Mix in half of buttermilk, along with oil and vanilla. Repeat with remaining half of flour and buttermilk, stirring until just incorporated.Pour batter into a parchment-lined 13×9-inch baking pan, then bake at 350 degrees F for about 25 minutes.

Oh fudge.

This frosting, y’all. Let’s just say that if you’re craving chocolate, this frosting alone would satisfy even the most intense cravings.

Because it is made with both dark chocolate and cocoa powder, the chocolate flavor is rich and bold and intense (I think of Bill Murray in Lost in Translation, when he’s filming the whisky commercial and the only feedback he receives is “more… intensity.” Well this frosting has that intensity, by way of multiple forms of chocolate.)

The preparation begins much like a typical ganache, though with a few more ingredients in addition to the cream and chocolate.

For frosting, whisk together sugar and cocoa powder in a small saucepan.Add cream, glucose syrup, and butter and bring to a simmer over medium heat.Pour hot cream-cocoa mixture over chopped chocolate in a heat-proof bowl.Let sit for 30 seconds, then gently whisk until chocolate is fully melted and smooth.Add room temperature sour cream to melted chocolate mixture.Gently whisk until frosting is shiny and smooth, then let cool, stirring every 5-10 minutes, until it holds soft peaks.Once frosting is cool enough to hold soft peaks, spread onto fully cooled cake.Use an offset spatula or the back of a spoon to make swoopy swirls as desired.Decorate as desired (I used a chocolate crisp pearl blend for texture and a fun appearance).

The frosting is smooth and almost pourable at first; if you wanted you could simply pour it on top of your cooled cake right in the baking pan and let it settle into a flat, even layer.

Or, do like I did, and let the frosting cool to room temperature, stirring it every 10 minutes or so to ensure it cools evenly. This will take about an hour until the frosting holds its shape and can be spread into swoopy swirls or even piped if you prefer. (You can speed up the process in the refrigerator, just set a repeating timer to remind yourself to give it a gentle stir every 5 minutes to ensure it cools evenly; it’ll thicken up quicker than you think it will).

The frosting on the cake.

There’s no denying this frosting is deeply, intensely chocolate. Which I love (the more chocolate the better, I say!) but I understand that it might not be everyone’s cup of tea.

If you’re wanting a lighter finish, but still chocolate, try my chocolate cloud frosting. It would be a perfect compliment to the moist and tender brown butter banana cake but with a lighter consistency and a more mellow chocolate flavor.

I also think my Nutella whipped ganache would be lovely with this cake as well (banana and hazelnut go so well together). It’s made with half semi-sweet and half milk chocolates, plus Nutella, so the chocolate isn’t quite as in-your-face.

Of course, some people are set on cream cheese frostings with banana cake, which is not my cup of anything, if we’re being honest, but hey, you do you. A vanilla-scented swiss meringue buttercream however, would be perfectly lovely (Pssst… did you know you can use brown butter in buttercream frostings? Just let it cool until it solidifies at cool room temperature and you can use it just like regular butter in most frosting recipes).

Ingredient Notes & Substitutions

Butter: I used a European style salted butter in this recipe as I wanted the brown butter to really shine, and the higher butterfat % in European style butters really makes a difference in the flavor. If you use unsalted butter, add an additional 1/4 teaspoon of salt to the cake.

Buttermilk: use full fat buttermilk if you can find it. In a pinch, you can substitute 2/3 cup whole milk mixed with 3 tablespoons of sour cream in place of the buttermilk (I’m not a fan of the lemon juice/vinegar swap).

Dark chocolate: I used a 70% dark chocolate for my frosting. If you use a chocolate with a lower cocoa %, you will end up with a looser frosting.

Cocoa Powder: I used Dutch process cocoa powder (Valrhona is my favorite, but Cacao Barry is a great option that’s a bit more affordable). Dutch process cocoa has a deep brown color and intense chocolate flavor. Natural cocoa will work here too, it’ll just produce a lighter colored frosting.

Sour cream: The sour cream adds tang and helps cut the sweetness of the frosting. Use full fat sour cream here; I do not recommend swapping low-fat or yogurt as it may cause the frosting to break.

Glucose syrup: An invert sugar helps the frosting stay smooth and shiny. I like glucose syrup as it’s not as sweet as other invert sugars, but it does need to be purchased online or from a specialty pastry shop. You can also use corn syrup or golden syrup instead (I think the flavor of honey would be too overpowering so I don’t recommend it).

Chocolate pearls: these crunchy little chocolate pearls in dark, milk, and caramelized chocolate make the perfect classy decoration with a subtle crunch that I adore. I can’t seem to find the mixed bag I purchased a few years ago, but you can still find the individual chocolate flavors online or in specialty pastry stores.