Luscious Chocolate Swirl Banana Cake

Try moist and luscious chocolate swirl banana cake with silky ganache frosting; it’s an easy recipe and perfect for a potluck. |

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We love bananas at our house, but it seems like there are always one or two (or three) that are forgotten behind a loaf of bread or a bag of tortilla chips and they end up all brown and squishy.  When I found two large ones in that sad state I thought about making strawberry banana walnut bread, but Joe mentioned earlier in the day that he was craving something chocolate.  I started looking through my cookbooks for inspiration and in my 25-year-old copy of Mrs. Fields Cookie Book I found a recipe for a luscious chocolate swirl banana cake that looked irrestible, so I threw it together, added a little twist of my own, and killed two birds with one stone.

The recipe is easy to make and can be done completely by hand, with a hand mixer, or in a stand mixer with the paddle attachment.  Beat the butter and brown sugar together, then add the mashed up banana and beat it some more until the mixture is smooth.  Add the sour cream, egg, and vanilla and beat until smooth again.  Dump in all of the flour that you already combined with the baking soda and mix it all on low until it’s combined.  Pour the melted chocolate in a stream over the top and carefully fold it in by hand just untiil you have a marbled effect, then pour the batter into the prepared baking pan and pop it into the oven.

Luscious chocolate swirl banana cake with silky ganache frosting is so easy to make, |
The melted chocolate is gently folded into the banana cake batter to get a delicious marbled effect.

Bake until a toothpick comes out clean, about 40 or 50 minutes, depending on what size pan you use.  I used an 8″ pan here and you can see that it’s pretty full, so I baked the cake for 45 minutes, then tested it with a toothpick that came out with a tiny bit of chocolate on it.  I was afraid that the cake wasn’t quite done in the middle, but it seemed to be on the verge of burning around the edges, so I turned off the oven and left the cake in for another 5 minutes and it was done perfectly.

That’s one of my “secret” techniques that I use to be sure I don’t overbake or burn cake or bread or whatever.  I tart visually checking progress through the window in the oven door when 75% of the recommended baking time is up, then every five to 10 minutes after that.  When it’s gone for the recommended time, if the baked item is getting suspiciously dark brown around the edges but the middle just doesn’t seem to be firm, or a toothpick doesn’t come out quite as clean as it should, or an instant read thermometer isn’t showing the temperature specified in the recipe, I’ll leave the pan in the turned-off oven with the door shut for another 5 to 10 minutes.  It works for me every time.

I set the cake in the pan on a rack for 15 minutes to firm up, then turned it out and set it upright on the cooling rack for a couple of hours.

Luscious chocolate swirl banana cake is an easy recipe that's perfect for a potluck. |
With just 1-1/4 cups of mashed banana from two large bananas, the batter baked up to fill the 8″ square pan, but didn’t overflow.

When the cake was nearly cool, I started on the ganache frosting.  I nuked heavy cream until it was steaming and started to bubble up, then I added the chocolate chips and let it sit undisturbed for 15 minutes.  I slowly stirred with a spoon until all the chips were melted and the mixture was smooth then put the uncovered bowl in the refrigerator for 30 minutes, stirring it a couple of times during that half hour.  I used our infrared thermometer and when the temperature of the frosting was 70°F and mounded without flowing, I put the cake on a serving plate and spread the frosting on the top and sides with a small offset spatula, swirling it a little on top to look pretty.  Oh man, that ganache was silky smooth and creamy and so hard to resist eating by the spoonful!


Silky ganache frosting for luscious chocolate swirl banana cake; perfect for a potluck. |
The chocolate ganache cools to become irresistibly smooth and creamy. When it cools to about 70°F, it will mound and spread evenly without dripping or flowing.

To “gild the lily” as my Mom used to say, I melted half a Baker’s white chocolate bar in the microwave, put it into an icing bag fitted with a writing tube and drizzled it ever so artistically (ha!) over the ganache.

Luscious chocolate swirl banana cake with silky ganache frosting, it's easy and so delicious. |
Melted white chocolate drizzled on the ganache frosting is an attractive finishing touch.

I got a knife and sliced into that cake right then and there!

Lluscious chocolate swirl banana cake with silky ganache frosting is an easy recipe. |
Sharing is caring, so share luscious chocolate swirl banana cake with your favorite people.

The sour cream and mashed bananas make this cake wonderfully moist, and the chocolate and banana make beautiful music together.  Topped with that silky ganache, this simple homey dessert is heavenly.

I added ice cubes to leftover coffee from breakfast to enjoy with this cake for a great afternoon pick-me-up.

An easy recipe that's perfect for a potluck is luscious chocolate swirl banana cake. |
Marbly chocolatey banana cake–YUMMMM!

Remember this recipe the next time time you discover squishy brown bananas hiding behind a bag of tortilla chips, or go ahead and buy bananas especially to treat yourself.

Make the recipe and discover that luscious chocolate swirl banana cake tastes as good as it looks.

Try moist and luscious chocolate swirl banana cake with silky ganache frosting; it’s an easy recipe and perfect for a potluck. |
Luscious chocolate swirl banana cake with silky ganache frosting; resistance is futile!

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Thanks, and bon appetit!

5.0 from 2 reviews
Luscious Chocolate Swirl Banana Cake
Prep time
Cook time
Total time
A moist, delicious cake for a potluck. If you're planning to serve the cake right out of the pan, use the 9"X9" pan to leave room for the frosting.
Recipe type: Cakes
Cuisine: American
Yield: 9-12 pieces
  • 2-1/2 cups (10-3/4 oz, 300 grams) all purpose flour
  • 1 tsp baking soda
  • 1-1/4 cups (9.5 oz, 266 grams) brown sugar, firmly packed
  • 1/4 cup (2 oz, 56 grams) salted butter, softened
  • 1/2 cup (4 fluid oz, 118 ml) full fat sour cream, room temperature
  • 1-1/4 cups to 1/2 cups (10 to 12 fluid oz, 296 to 355 ml) mashed banana (2 or 3 large)
  • 1 large egg, room temperature
  • 1 tsp pure vanilla extract
  • 3/4 cup (4-1/2 oz, 126 grams) semisweet chocolate chips, melted and cooled
Ganache Frosting
  • 3/4 cup (6 fluid oz, 177 ml) heavy cream
  • 1 cup (6 oz, 170 grams) semisweet chocolate chips
Optional Decoration
  • 2 oz (56 grams) white chocolate baking bar, broken
  1. Preheat oven to 350°F.
  2. Spray an 8" by 8" or 9" by 9" baking pan with non-stick baking spray
  3. In medium bowl, combine flour and baking soda and mix with a wire whisk; set aside.
  4. In a large bowl, blend the brown sugar and butter with a hand mixer or stand mixer, then scrape the sides of bowl.
  5. Add the banana and beat on medium until the mixture is smooth.
  6. Add the sour cream, egg, and vanilla and beat again on medium until smooth.
  7. Add the flour mixture all at once and blend on low until just combined, don't overmix.
  8. Pour the the melted chocolate in a stream over the top of the mixture and fold it in by hand just a few turns until the mixture is marbled.
  9. Pour the batter into the prepared pan.
  10. Bake 40-50 minutes until a toothpick inserted in the center comes out clean.
  11. Remove the pan from the oven and set it on a cooling rack for 15 minutes to allow the cake to firm up a bit, then turn the cake out of the pan and place it right side up on the cooling rack; cool to room temperature.
Ganache Frosting
  1. Microwave the heavy cream in a small microwave-safe bowl for 1 to 2 minutes until it's steaming, then add the chocolate chips and set aside for 10 to 15 minutes.
  2. Stir ganache until it is smooth, then refrigerate uncovered, 30 to 40 minutes, stirring once or twice.
  3. When it's reached about 70°F, the ganache should mound and be spreadable without flowing.
  4. Frost the cake top and sides with the ganache.
Optional Decoration
  1. Melt 2 oz of white chocolate in a microwave for 60 to 90 seconds, stirring every 30 seconds until it's completely melted.
  2. Pour into a disposable icing bag or plastic quart bag and cut off a corner.
  3. Drizzle decoratively over the top of the frosted cake.
The amount of mashed banana is fairly flexible in this recipe. I only had two bananas and the quantity when mashed was about 1-1/4 cups. But you can use up to 1-1/2 cups of mashed bananas.
The cake may be made a day ahead, but cover and refrigerate leftovers.


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