This Banana Birthday Cake with Chocolate Frosting is the perfect dessert for any celebration! Tender banana cake layers with fluffy chocolate buttercream!
Preheat your oven to 350 degrees Fahrenheit and prepare two 8-inch cake pans by greasing and flouring them and placing a circle of parchment paper in the bottom of each pan. Set aside.
In the bowl of your stand mixer fitted with the paddle attachment (or in a large bowl with a hand mixer), beat the butter and granulated sugar on medium high speed for a few minutes until fluffy.
Add the eggs one at a time, beating well after each addition.
Beat in the mashed bananas on medium speed, scraping down the sides of the bowl to make sure everything is combined.
Measure out the buttermilk and set it aside.
Measure the flour, baking powder, baking soda, and salt into a separate bowl and add it to the butter mixture on low speed in 3 additions, adding half the buttermilk in between each addition of the dry ingredients.
Mix on low speed just until a batter forms and scrape down the sides of the bowl to ensure everything is incorporated.
Divide the batter between the two prepared pans and smooth out the tops.
Bake at 350 degrees Fahrenheit for anywhere from 24-29 minutes, or until a toothpick inserted into the middle of the cakes comes out clean.
Cool the cakes in their pans for about 10 minutes and then turn them out onto a cooling rack to finish cooling completely.
In a large bowl with a hand mixer, or in the bowl of your stand mixer fitted with a paddle attachment, beat the butter on high speed until smooth.
Add the cocoa powder and powdered sugar gradually, about 1/2 cup at a time, mixing on medium high speed until smooth. Add the salt at this time as well.
Continue mixing on medium high speed, adding the heavy cream one tablespoon at a time until a soft, spreadable consistency is reached. Whip on high speed to make the frosting ultra fluffy once the heavy cream has been added.
Assemble the cake by peeling the parchment paper off the cooled cake layers. Place one cake layer bottom side down on a cake stand or large plate.
Dollop about 1 cup of frosting on top of this layer (level the layer first with a serrated knife, if necessary) and spread it out in an even layer.
Add the second cake layer upside down (level this layer as well, if you wish) and spread the remainder of the frosting over the top and sides of the cake using a rubber spatula, a butter knife, or an offset spatula.
Make rustic-looking swirls on the cake as you frost it, and top with sprinkles if desired.
Refrigerate until ready to serve, or serve immediately. The cake slices best after refrigerating for about 30 minutes.