I knew we had a winner after the first bite of this rich chocolate banana cake. Tender chocolate banana cake layers—made with ripe bananas and a chocolate cake mix—and my favorite cocoa buttercream come together to make a cake that’s straightforward, comforting, and absolutely delicious.
Keeping with the classics
This isn’t a cake loaded with multiple textures, fillings, or fancy elements, and that’s the point. Stripping things back doesn’t make it basic—it makes it a reliable, go-to classic. Simple cakes like this are approachable, fast, and exactly what you want when you crave a genuinely good chocolate banana cake.
I do love experimenting with crusts, fillings, and layers, but sometimes you want something that’s easy to make and universally loved. If you have a few ripe bananas and a chocolate cake mix, you can have this cake ready in under 40 minutes from start to finish.
Meet your new favorite chocolate banana cake—moist layers studded with mini chips and filled with a silky cocoa buttercream. It’s exactly the kind of cake you’ll want again and again.
How to doctor up a cake mix into a chocolate banana cake
If you’ve been here a moment, you know I love transforming cake mixes into something that tastes homemade. Using a boxed mix saves time and reduces the chance of mistakes, but adding a few ingredients makes the flavor and texture feel like scratch baking.
For this recipe, add the following to your chocolate cake mix to create tender, flavorful layers that rival from-scratch cakes:
- Buttermilk
- Eggs
- Sour cream
- Ripe bananas
- Vanilla
- Vegetable oil
- Mini chocolate chips
Ignore the water/egg/oil instructions on the cake mix box—use the recipe quantities below for the best result. Sifting the cake mix into the batter helps achieve a silky, even crumb.
Which cake mix should I use?
I prefer Duncan Hines Dark Chocolate Fudge for the deep chocolate flavor, but any good-quality chocolate cake mix around 15.25 oz will work. Sift the mix into your wet ingredients and you’ll get the smoothest texture.
The best cocoa buttercream
This cocoa-based buttercream is my go-to. It’s rich, easy to make, and pairs perfectly with the chocolate banana layers. Unlike a ganache-style frosting, this buttercream uses cocoa powder, which many home bakers already have in the pantry.
One thing to remember: cocoa powder soaks up liquid quickly, so the frosting can thicken fast. Don’t be afraid to add extra heavy cream to reach the ideal spreadable consistency. If it gets too thin, add a little more powdered sugar; if it’s too thick, add small amounts of cream until it’s just right.
Look at that slice—tempting, right? This cake is worth a second helping. I certainly enjoyed a few slices while testing the recipe.
Texture cake scraper
A textured cake scraper on the sides adds a professional touch with minimal effort. Using a patterned scraper creates visual interest without needing perfectly smooth edges—great for a rustic, homemade finish.
6″ or 8″ cake rounds?
This recipe works for three 6″ rounds, two 8″ rounds (taller), or three 8″ rounds (thinner). I usually bake three 6″ or two 8″, but tried three 8″ for these photos. They were a bit shorter than usual but still delicious with layers of buttercream between them. Choose the size that fits your occasion.
Video tutorial
If you prefer a visual guide for making the cocoa buttercream, there’s a short video demonstrating the process. Seeing the frosting come together can make it easier to judge consistency as you go.
I can’t wait for you to bake this chocolate banana cake. It’s moist, chocolatey, and perfect for sharing. If you make it, I’d love to see your photos—tag me on social media so I can enjoy your creations with you.
Happy baking!
xo,
Mandy
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The Best Chocolate Banana Cake
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Ingredients
Chocolate Banana Cake
- 3/4 cup buttermilk, room temperature
- 1/3 cup sour cream, room temperature
- 3 whole large eggs, room temperature
- 2-3 medium ripe bananas, the more brown the better
- 1/3 cup vegetable oil
- 1 Tablespoon vanilla
- 1/2 cup mini chocolate chips, optional
- 1 15.25oz chocolate cake mix, I used Dark Chocolate Duncan Hines
Cocoa Buttercream
- 1 1/2 cup (or 3 sticks) unsalted butter, left at room temperature about 10 minutes
- pinch of salt
- 1 Tablespoon pure vanilla
- 1/2 + 1/2 cup heavy cream (plus an extra 1/2 cup to thin if needed)
- 1/2 cup quality cocoa powder
- 7 cups powdered sugar
Extras
- 1 cup mini chocolate chips
Equipment
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inverted scallop cake scraper
Instructions
For the Banana Chocolate Cake
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This recipe can be made into three 6″ cake rounds, two 8″ cake rounds (thick), or three 8″ cake rounds (thin). Prep pans with a light swipe of shortening and a dusting of flour.
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Preheat oven to 325°F on convection. If using conventional bake, increase baking time by 2–3 minutes as needed.
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In a large bowl, whisk together all wet ingredients except the mini chips and cake mix. Stir in the mini chips, then sift the cake mix into the bowl and fold gently. Divide batter between prepared pans and bake 20–25 minutes, or until a toothpick comes out clean.
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Invert pans onto a wire rack to cool. Once cooled, wrap layers in plastic and store in the freezer until ready to assemble.
For the Cocoa Buttercream
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In a stand mixer with the paddle attachment, whip the butter until light and fluffy. Scrape the bowl as needed.
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Add a pinch of salt, vanilla, 1/2 cup heavy cream, and the cocoa powder. Mix until combined.
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Gradually add powdered sugar, about 1/2 cup at a time. The mixture may become powdery—then add the final 1/2 cup heavy cream to bring it together into a smooth buttercream.
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Beat on high for 2 minutes. Adjust consistency with small amounts of heavy cream if too thick, or additional powdered sugar if too thin.
Assembly
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Place a small dollop of buttercream on a cardboard cake round to secure the first layer. Spread a thin layer of frosting, add the next cake layer, and repeat.
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Crumb coat the cake and freeze for about 3 minutes to set the crumb coat.
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Stir the buttercream by hand briefly to remove air bubbles before applying the final layer of frosting. This helps achieve a smoother finish.
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Spread the remaining buttercream, create a decorative swirl on top with an offset spatula, and use a cake scraper (inverted scallop here) for textured sides. Leave the top a bit rustic if desired.
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Garnish the outer rim with mini chocolate chips and serve. Enjoy!