Chocolate Peanut Butter Layer Cake

Here is a list of things about this cake that didn’t turn out the way I originally intended: 1) shape, 2) size, 3) decoration, and 4) photos. Thankfully, ‘taste’ is not one of them. It definitely met my expectations for taste, but first – everything that went wrong:

(1) I don’t have three 8-inch round cake pans and my mom really was not going to buy me any more baking stuff. Fine, I thought, a rectangular cake would be unique…Long story short, I found out the hard way that a somewhat normal-looking rectangular cake is really hard to build from my pan options of 8×8 and 9×13. (2) On top of that, I was running out of the house on Friday night just when the cakes had gotten out of the oven, and my mom wasn’t home early enough to turn the layers out onto cooling racks, so they sank quite a bit.

Moral of the story – I’m going to share with you the original recipe as it is in the Baking Illustrated cookbook, which yields 2 9-inch round layers. Personally, I think the width-to-height ratio of a two-layer 9-inch cake isn’t very pretty, which is why I wanted 3 8-inch round layers to begin with. At the end of the day though, it all tastes the same in your tummy 🙂 Don’t be afraid to make adjustments; I just thought it would be easiest to go from the original quantities.

This is a very dense, fudgey cake that my mom and I love because we both prefer a darker chocolate cake over a lighter, spongier one. The secret to the intense flavor is mixing the cocoa powder and instant coffee in boiling water – it gives it depth and enhances the chocolate flavor. (Am I the only one who is always tempted to spell things the British way? ‘colour’ and ‘flavour’ just look better than their American spelling counterparts…)

On to failure part (3): I’ve only ever frosted round layer cakes, like the Red Velvet Cheesecake Cake. It didn’t really occur to me that I got such a smooth finish because of the lazy susan I turned the cake on, and it turns out rectangular cakes are much harder to get smooth without an offset spatula! I resorted to the technique where you press the back of a spoon into the frosting and pull straight up, forming a peak. Does this technique have a name? How about the ‘Super Easy Swirly Technique That Makes It Look Like A Lot More Work Than It Actually Is‘?

I also intended to whisk away a slice of the cake to take pictures of at the party, but I didn’t have my camera with me and Mayline (who along with her husband Kenneth helped me design this website) arrived too late for me to steal her camera before the cake was all gone, so (4) enjoy the impeccable quality of these pictures from my friends’ cellphone cameras:

I heard that it tasted just like a Reese’s Cup! This peanut butter frosting is pretty darn good, not too salty and not too sweet and kind of melts in your mouth. Chocolate and peanut butter is my second favorite flavor combination, right after mint and chocolate. And then after that comes coffee and chocolate… are you starting to see a pattern here?

Recipe: Sour Cream Fudge Layer Cake


  • 1 1/4 C all-purpose flour, plus more for dusting pans
  • 1 C natural cocoa (unalkalized)
  • 2 tsp instant espresso or coffee powder
  • 1 C boiling water
  • 1/2 C sour cream
  • 2 tsp vanilla extract
  • 2 sticks (16 TB) unsalted butter, softened but still cool
  • 1 2/3 C sugar
  • 2 large eggs, room temperature
  • 1/2 tsp salt


  1. Preheat to 350 degrees F and position the oven rack in the middle. Grease 2 9-inch round cake pans and cover the bottoms with parchment paper. Grease the parchment and dust with flour, tapping out excess.
  2. In a small bowl, mix cocoa and instant espresso and add the boiling water. Mix until smooth, then stir in the sour cream and vanilla when cooled to room temperature.
  3. Beat the butter until smooth and shiny, then add the sugar slowly. Beat until the mixture is light and fluffy, 3-5 minutes. Add the eggs one at a time, beating 1 full minute after each addition.
  4. Whisk the flour, baking soda, and salt in a medium bowl. With the mixer on low speed, add the dry ingredients in three additions alternating with the sour cream mixture, beating each addition just until incorporated. Scrape down the sides of the bowl and beat until the batter looks satiny.
  5. Divide the batter evenly between the prepared pans. Bake the cake layers for about 23-30 minutes or until a toothpick inserted in the center comes out clean. Transfer the baked cake layers to a wire rack and let cool in the pans for 10 minutes before inverting onto the rack to cool completely and peeling off the paper liners. Cool completely before frosting.


Whenever I make layer cakes, I bake the cakes the day before. Once they’re cool, I wrap them tightly in plastic wrap and foil, then refrigerate them overnight. This makes the layers a lot easier to frost and fill the next day!


According to my calculations, you can increase all the ingredients by 1/3 for 3 9-inch layers, or by 1/4 for 3 8-inch layers. Let me know how your adjustments work for you in the comments below!

Number of servings (yield): Makes 2 9-inch round layers

Adapted from Baking Illustrated

Recipe: Peanut Butter Frosting


  • 2 cups confectioners’ sugar
  • 1 2/3 cup creamy peanut butter
  • 10 tablespoons unsalted butter, at room temperature
  • 1 teaspoon vanilla extract
  • ¼ teaspoon kosher salt
  • 2/3 cup heavy cream


  1. Make the frosting: Place the confectioners’ sugar, peanut butter, butter, vanilla and salt in the bowl of an electric mixer fitted with a paddle attachment. Mix on medium-low speed until creamy, scraping down the bowl with a rubber spatula as you work. Add the cream and beat on high speed until the mixture is light and smooth.
  2. To frost and fill the cake: Even out your layers by using a long serrated knife to saw off the dome, if needed. Place a generous dollop of frosting in the center of your first layer and smooth it out, leaving about a half-inch border unfrosted (the second layer will push the frosting out). Repeat with remaining layers. Crumb coat your cake and refrigerate for about 20 minutes, or until the frosting no longer comes off on your finger when you touch it. Now you are ready to finish off the top and sides of the cake – again, start with a ton of frosting on top, and spread it out with a spatula so it hangs a little over the edge. Smooth the rest of the frosting around the sides, using a turn table or lazy susan to help if the cake is round.
  3. Decorate as desired. To make the peaks like in the rectangular cake, press the back of a spoon into the frosting and pull straight up, forming a peak and repeat all over the surface.

Number of servings (yield): Should be enough to fill and frost 3 layers

Adapted from Barefoot Contessa at Home by Ina Garten

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