Peanut butter and chocolate are a classic pairing—and this cake doubles down on chocolate with rich chocolate cake layers plus a fudgy chocolate ganache. A thick layer of silky peanut butter Swiss-style buttercream sits between the ganache layers for the ultimate chocolate-peanut butter experience. If you love that combo, this fudgy chocolate peanut butter cake delivers deep chocolate flavor and creamy peanut butter frosting in every bite.
Why This Is the Best Chocolate Peanut Butter Cake
Few flavor combinations are as beloved as chocolate and peanut butter. This recipe elevates that pairing by combining a moist, deeply chocolate cake with a fudgy ganache layer and a smooth Swiss-style peanut butter buttercream. Each component—cake, ganache, and frosting—is a favorite on its own; together they create a multi-layered dessert with rich chocolate intensity and creamy peanut butter balance. The result is a decadent, well-balanced cake that stays tender and flavorful.
Ingredient Notes to Make the Best Cake
- Dutch-Processed Cocoa Powder: Use Dutch-processed cocoa for a deep, dark color and mellow chocolate flavor without extra acidity.
- Hot Coffee: The hot liquid helps the cocoa bloom, intensifying the chocolate flavor and producing a velvety crumb. The cake won’t taste like coffee.
- Buttermilk: Buttermilk keeps the cake moist and tender—the acidity reacts with baking soda for a lighter crumb and longer freshness.
- Creamy Peanut Butter: Choose a stable creamy peanut butter (such as mainstream brands) for a smooth, non-grainy buttercream. Natural peanut butters can separate and affect texture.
Tips for the Perfect Fudgy Ganache
The ganache provides the fudgy chocolate layer in this cake. To avoid it being too thin, too runny, or becoming hard and grainy, chill it until firm but still spreadable. Check and stir every 20–30 minutes while it cools. If the ganache is too soft, the buttercream may slide; if chilled too long it can become grainy. Aim for a spreadable, slightly firm consistency for best assembly results.
Frequently Asked Questions (FAQ) – Fudgy Chocolate Peanut Butter Cake
Can I make this as a layer cake instead of a sheet pan?
Yes. While the recipe is written for a 16×10 sheet pan, you can bake the batter in two 8-inch round pans. If you cut those rounds in half you’ll get four thinner layers rather than three, so the frosting layers will be slimmer. Watch the bake time—deeper or smaller pans may need a few extra minutes.
Does this cake need to be refrigerated?
Because the ganache contains heavy cream and the buttercream uses egg whites, store the finished cake in the refrigerator. It’s best on the day it’s made and can sit at room temperature for a few hours depending on ambient temperature. For optimal texture, let slices warm at room temperature for 15–20 minutes before serving so the frosting softens.
Why is my buttercream curdling?
If the buttercream looks curdled after adding butter, keep whisking—the emulsion usually comes back together after a few minutes on medium-high speed, resulting in a silky, smooth frosting.
Peanut Butter Fudge Cake
Ingredients
Chocolate Cake:
- 1 ¾ cups all-purpose flour 210 g
- 2 cups granulated sugar 400 g
- ¾ cup unsweetened cocoa powder, preferably Dutch-processed 75 g
- 2 teaspoons baking soda 10 ml
- 1 teaspoon baking powder 5 ml
- 1 teaspoon salt (1/2 teaspoon if Morton) 5 ml
- 2 large eggs
- 2 teaspoons vanilla extract 10 ml
- 1 cup buttermilk 240 ml
- ½ cup oil (canola or vegetable) 120 ml
- 1 cup hot coffee 240 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
Chocolate Ganache:
- 5 oz chocolate
- 4 tablespoons butter 57 g
- 3/4 cup sugar 150 g
- 3/4 cup heavy cream 180 ml
- 2 teaspoons vanilla 10 ml
- Pinch of salt
Instructions
Cake:
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Whisk together sugar, flour, cocoa powder, baking soda, baking powder, and salt until evenly combined.
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Add vanilla, eggs, buttermilk, and oil and stir until combined.
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Stir in the hot coffee quickly so it is evenly distributed. The batter will be thin.
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Pour the batter into a greased and floured 16×10″ sheet pan. Bake at 350°F for about 15–20 minutes, or until a toothpick inserted in the center comes out clean.
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Set the cake aside to cool completely before assembling.
Ganache:
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Place chocolate, butter, salt, and vanilla in a bowl. In a small saucepan over medium heat, warm the cream and sugar until hot but not boiling.
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Pour the hot cream and sugar over the chocolate mixture and let sit for 1 minute, then stir until smooth.
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Chill the ganache in the refrigerator until cooled and firm but still spreadable—about 30 minutes to 1 hour. It should be firm enough to support the frosting.
Peanut Butter Buttercream:
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Cut softened butter into tablespoon pieces.
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Set 2 inches of water in a saucepan and bring to a simmer. Place a heatproof bowl over the pan (bowl should not touch the water). Add sugar, egg whites, and salt to the bowl and whisk while heating until the sugar dissolves and mixture reaches about 120°F.
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Transfer the bowl to a stand mixer and whip on high until the mixture is thick, glossy, and holds stiff peaks.
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Reduce mixer speed to medium and add butter one tablespoon at a time until incorporated. Lower speed to add peanut butter, then increase to medium until smooth. Set aside.
Assembly:
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When all components are ready, cut the cooled cake into three equal rectangular layers.
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Spread a thin layer of ganache on the first layer (you can pipe a ganache border to contain the buttercream). Spread about half the peanut butter buttercream over the ganache. Repeat with the next layer and remaining buttercream. Finish with a thin top layer of ganache. Trim edges for a clean rectangular presentation; leaving the sides exposed is optional.
