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.
Recipe by MJ Bakes A Lot at