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peanut butter brown sugar layer cake with chocolate fudge buttercream and chocolate ganache drip
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4.78 from 9 votes

Peanut Butter Brown Sugar Layer Cake with Chocolate Fudge Buttercream

The Peanut Butter Cake to end all other peanut butter cakes. AKA a moist as heck peanut butter brown sugar cake with a sinful chocolate fudge buttercream frosting. From Michelle Lopez's (@hummingbirdhigh) new cookbook: Weeknight Baking.

Prep Time40 mins
Cook Time45 mins
Total Time1 hr 25 mins
Course: Dessert
Cuisine: American
Keyword: Cakes & Cupcakes, Chocolate Fudge Frosting, Peanut Butter Cake
Servings: 10 slices
Calories: 1084.72kcal
Author: Mike Johnson


For the Peanut Butter Brown Sugar Cake:

  • 280 g cake flour
  • 440 g dark brown sugar
  • teaspoon baking powder
  • teaspoon baking soda
  • teaspoon coarse sea salt
  • 255 g unsweetened creamy natural peanut butter
  • 240 g buttermilk
  • 190 g water
  • 110 g vegetable oil
  • 2 large eggs
  • 2 teaspoon vanilla extract

For the Chocolate Fudge Frosting:

  • 170 g dark chocolate (70%+ cacao), chopped
  • 480 g powdered sugar
  • 340 g unsalted butter at room temperature
  • 1 tablespoon vanilla extract
  • ¼ teaspoon coarse sea salt
  • 60 g milk


  • Preheat oven to 350°F (177°C). Grease two 8-inch cake pans, line with parchment paper, then grease the parchment paper. (Parchment paper helps the cakes seamlessly release from the pans.)

  • Make the cake: Whisk the flour, dark brown sugar, baking powder, baking soda, and salt together in a large bowl. In a separate bowl, whisk the peanut butter, buttermilk, water, oil, eggs, and vanilla until the mixture is smooth and caramel in color. Gradually add the dry ingredients and whisk until just combined.

  • Pour the batter into the prepared pans and bake for 45 to 50 minutes or until the tops of the cakes spring back when gently touched and a toothpick inserted in the center comes out clean. If the cakes need a little longer as determined by wet crumbs on the toothpick, bake for longer. However, careful not to overbake as the cakes may dry out. Remove cakes from the oven and cool completely in the pans set on a wire rack. The cakes must be completely cool before frosting and assembling.

  • Make the frosting: Place the chopped chocolate in a heatproof bowl and set over a pan of gently simmering water to create a double boiler. Stir occasionally until the chocolate is fully melted. Remove the bowl from the heat and set aside on a wire rack to cool slightly.

    In the bowl of a stand mixer fitted with the paddle attachment, beat the butter on medium-high speed until smooth, about 2 minutes. Add the powdered sugar, milk, vanilla extract, and salt. Beat on low speed for 30 seconds, then increase to high speed and beat for 2-3 minutes until completely combined. Add in the melted chocolate and beat on high speed for another 1-2 minutes until fluffy and completely combined. Add more confectioners’ sugar if frosting is too thin, more milk if frosting is too thick, or an extra pinch of salt if frosting is too sweet. Frosting should be soft and creamy, but not runny.

  • Assemble and frost: Using a large serrated knife, slice a thin layer off the tops of the cakes to create a flat surface. Place 1 cake layer on your cake stand or serving plate. Evenly cover the top with frosting. Top with 2nd layer and spread remaining frosting all over the top and sides. I used an offset icing spatula and bench scraper for the frosting; a chocolate ganache for the drip; and a Wilton piping tip #2D for decoration around the top.

  • Refrigerate cake for at least 30-60 minutes before slicing. This helps the cake hold its shape when cutting.


Store leftovers in an airtight container in the fridge.


Serving: 1slice | Calories: 1084.72kcal | Carbohydrates: 126.39g | Protein: 13.57g | Fat: 61.07g | Saturated Fat: 34.16g | Cholesterol: 109.69mg | Sodium: 752.48mg | Potassium: 496.94mg | Fiber: 4.08g | Sugar: 97.98g | Vitamin A: 954.38IU | Calcium: 137.72mg | Iron: 3.3mg