Peanut Butter Cup Chocolate Layer Cake

This peanut butter cup chocolate layer cake starts with 3 layers of buttermilk chocolate cake layers. After the layers cool, we layer on peanut butter icing. This peanut butter icing is a Swiss meringue buttercream, but peanut butter gets added at the end. Once the cake is frosted, we top it with mini peanut butter cups. We love this cake so much that we made it for Jules’ birthday this year. It’s a peanut butter and chocolate lovers dream.

Why You’ll Love This Peanut Butter Chocolate Cake

• Three buttermilk chocolate layers: This cake starts with our go-to buttermilk chocolate cake. It is a version of the classic Black Magic Cake. It is moist and flavorful thanks to both the hot coffee and buttermilk in the batter.
• Peanut butter Swiss meringue buttercream: We make a Swiss meringue buttercream and then mix in creamy peanut butter so the frosting has tons of peanut butter flavor
• Mini peanut butter cups: We finish the cake with mini peanut butter cups, so there is a little peanut butter cup in every bite
• A tried-and-true birthday cake: We made this for Jules’ birthday this year, and it’s now on regular rotation for us. It’s perfect for a peanut butter and chocolate lover.

Frequently Asked Questions

Can I make this peanut butter chocolate cake ahead of time? Yes. Bake the cake layers a day in advance and tightly wrap in plastic wrap. Then assemble the cake the day you plan to serve it for the freshest result.

What’s the difference between Swiss meringue buttercream and regular buttercream? Swiss meringue buttercream is made by warming egg whites and sugar before whipping and adding butter, which creates a silkier, less sweet frosting than a traditional powdered-sugar American buttercream.

Can I substitute natural peanut butter in the buttercream? We recommend sticking with a classic, shelf-stable creamy peanut butter like Skippy. Natural peanut butter has a higher oil content and can make the buttercream separate or turn oily.

Can I make this cake in round pans instead of a sheet pan? Yes, though you’ll need to adjust baking time since round pans will bake for a bit longer than the thinner sheet pan layers. Keep testing with a toothpick until it comes out clean.

How many layers does this cake have? The recipe makes enough batter for three chocolate cake layers, each spread with peanut butter Swiss meringue buttercream.

Print

Peanut Butter Cup Chocolate Layer Cake

Prep Time 1 hour hour

Cook Time 30 minutes minutes

Cooling 1 hour hour

Total Time 2 hours hours 30 minutes minutes

Servings 12

Ingredients

Black Magic Cake (see note on origin below)

• 2 2/3 cups flour 320 g
• 3 cups sugar 600 g
• 1 1/8 cup cocoa 135 g
• 1 tablespoon baking soda 17 g
• 1.5 teaspoon baking powder 6 g
• 1.5 teaspoon salt 5 g
• 3 eggs
• 1 tablespoon vanilla extract 15 ml
• 1.5 cup buttermilk 350 ml
• .75 cup oil canola or vegetable 175 ml
• 1.5 cup hot coffee 350 ml

Peanut Butter Buttercream:

• 8 ounces salted butter room temperature
• 8 ounces granulated sugar
• 4 ounces egg whites
• ½ teaspoon salt
• 3/4 cup creamy peanut butter we used skippy 200 g
• 1 cup mini peanut butter cups for topping

Instructions

Cake

• Combine the sugar, flour, cocoa powder, baking soda, baking powder, and salt into a bowl. Stir together with a whisk until evenly combined
  
• Add the vanilla, eggs, buttermilk, and oil and stir until combined
• Once combined, add the hot coffee. Stir quickly to ensure the hot coffee is evenly distributed. The batter will be very thin
  
• Pour the batter into a greased and floured 16”x10” sheet pan and cook for ~15-20 minutes (ovens vary so test with a toothpick in the center and remove when it comes out clean) 350 F – make sure a toothpick comes out clean
  
• Set aside to cool
  
• Peanut Butter Buttercream:
• Cut the softened butter in tablespoon pieces.
• Add 2 inches of water into a saucepan that fits the bowl of a stand mixer on top without touching the water. After the water is simmering, add the sugar, egg whites, and salt. Whisk to combine and continue to simmer, ensuring the water does not touch the bowl. Keep heating the mixture until the sugar is dissolved (it will be about 120 degrees)
• Place the bowl in the stand mixer and whisk on high speed until mixture is thick and glossy. It should hold very stiff peaks.
• Reduce the speed of the mixer to medium and add the butter one tablespoon at a time until incorporated. Reduce the speed to low and add the peanut butter. Turn up the speed to medium until well incorporated. Set aside

Assembly

• When all components are ready, spread a layer of the peanut butter icing in between each layer. Coat the entire cake with the remaining peanut butter icing and top with peanut butter cups

Notes

Cake recipe based off of the classic “Hershey’s Black Magic Cake”