I’ve got a super simple single layer frosted cake today! If you love the classic combo of peanut butter and chocolate, this cake is for you. Fluffy chocolate cake topped with a peanut butter chocolate frosting is your sweet little treat for the weekend!

Peanut Butter Chocolate Cake

I’m a big fan of simple cakes that don’t involve layering or stacking, and this cake is the perfect recipe to scratch your itch for cake without all the work of a big 3-layer version. Let’s get to making the perfect Peanut Butter Chocolate Cake!

How to Make Peanut Butter Chocolate Cake

We’re starting off with a simple chocolate cake recipe. In your main large bowl, start by whisking together the dry ingredients. Then we’re going to melt butter, and heat it with water until the mixture is boiling before whisking in some dutch-processed cocoa powder. This process is called blooming the cocoa powder, and it helps to really bring out that chocolatey flavor!

Then start to whisk the cocoa mixture into the dry ingredients until it’s starting to come together. It will be very thick at this stage, and it doesn’t have to be mixed perfectly yet. Finally add in the buttermilk, egg, and vanilla extract and whisking until a smooth batter forms.

I like to bake this cake in a square pan for perfect little squares of cake, but you can also use a round pan if you prefer. Off to the oven until a toothpick inserted into the center of the cake comes out with just a couple of crumbs stuck to it.

The peanut butter chocolate frosting is a variation of American buttercream, and it’s pretty simple to whip up. I’ve some tips and tricks below to help. Once your cake is cooled, frost it and enjoy!

Tips & Tricks for Your Peanut Butter Chocolate Cake

Here are all my tips to help you make the perfect Peanut Butter Chocolate Cake!

  • How do you measure your flour? I typically scoop measure my flour without much fluffing. This results in 1 cup of flour weighing about 130-135 grams.
  • Why is the mixture so thick after adding the chocolate? This is just part of the liquid ingredients being added to the batter, but the batter will become smooth after adding the egg and buttermilk.
  • How do I know when the batter is fully mixed? You should have no pockets of dry flour in the batter, and it should be pretty smooth. I like to mix it with a whisk by hand to avoid over-beating the batter.
  • How do I know when my chocolate cake is baked? Your cake is baked when it looks puffed and set on top, and a toothpick inserted into the center of the cake comes out with just a couple of crumbs.
  • What if my buttercream mixture is too thick? You can add more heavy cream as needed to thin out the buttercream until it reaches your desired consistency.
  • What if my buttercream has separated and broken? You can pop the bowl in the fridge for 5 minutes and re-whip, repeating this process 2-3 times. If the mixture is still broken, add an addition 2 oz of melted, cooled chocolate to help stabilize the mixture.
  • I’m at about 5,000 ft. above sea level and I find that most people who live between about 3,000-7,000 ft above sea level do not need to make adjustments to my recipes.


Peanut Butter Chocolate Cake

Servings 9 slices


For the cake:

  • 1 1/4 cups all-purpose flour
  • 3/4 cups granulated sugar
  • 1/4 teaspoon baking soda
  • 1 teaspoon salt
  • 1/2 cup unsalted butter
  • 1/2 cup water
  • 1/4 cup dutch processed cocoa powder
  • 1/4 cup buttermilk
  • 1 large egg
  • 1 teaspoon vanilla extract

For the frosting:

  • 4 oz dark chocolate
  • 1/4 cup butter
  • 1/3 cup peanut butter
  • 2 cups powdered sugar
  • 1/4 tsp. salt
  • 1 tsp. vanilla extract
  • 1/4 cup heavy cream


For the cake:

  1. Preheat your oven to 350 degrees and grease an 8 inch square cake pan. Optionally line the pan with parchment paper and set aside. In a large bowl, whisk together the flour, sugar, baking soda, and salt. In a microwave safe medium bowl, melt the butter until just melted in the microwave, about 2 minutes. Then add in the water, and microwave for another minute, or until the mixture is just boiling. Stir in the cocoa powder and whisk to combine until smooth.
  2. Pour the chocolate mixture over the dry ingredients, and whisk until combined- the mixture will be very thick at this point. Then stir in the buttermilk, egg, and vanilla extract and whisk until combined and smooth. Pour the batter into your prepared cake pan, and bake for 30-35 minutes, or until a toothpick comes out with just a few crumbs clinging to it. Cool the cake completely before frosting it.

For the frosting:

  1. Melt the chocolate in the microwave, stirring every 30 seconds, until it is completely melted, about 1-2 minutes, and set this aside to cool. In a medium bowl, beat together the butter and peanut butter until smooth. Add in the powdered sugar slowly, and begin to mix until it starts to combine. The mixture will be very thick and crumbly at this stage. Mix in the salt, vanilla extract, and 2 tbs. of the heavy cream until combined. Then beat in the melted chocolate until mixed through. If the frosting is still too thick, beat in the remaining heavy cream until just combined, and the frosting becomes thick. Frost your cooled cake and enjoy!

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