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Horizontal image of a portioned whole dessert in a metal pan topped with frosting.

Sourdough Chocolate Cake with Peanut Butter Frosting

  • Author: Meghan Yager
  • Total Time: 3 hours, 55 minutes
  • Yield: One 9-by-13-inch cake 1x


This sourdough chocolate cake with peanut butter frosting is a delightful way to use up any extra sourdough starter you may have on hand.



For the Cake:

  • 1 cup sourdough starter
  • 1 cup milk (whole or 2%) 
  • 2 cups all-purpose flour 
  • 1 1/2 cups granulated sugar
  • 1 cup vegetable oil
  • 2 teaspoons vanilla extract
  • 1 teaspoon salt
  • 1 1/2 teaspoons baking soda
  • 3/4 cup natural cocoa powder 
  • 2 large eggs

For the Frosting:

  • 1 cup unsalted butter, softened to room temperature 
  • 1 1/4 cups creamy peanut butter, room temperature
  • 3 cups powdered sugar 
  • 1 teaspoon vanilla extract
  • 1/4 teaspoon salt
  • 2 tablespoons milk, plus more if needed


To Make the Cake:

  1. Add starter, milk, and flour to a large mixing bowl. Stir to combine. Cover with plastic wrap and let rest at room temperature for 2-3 hours. It should expand by a third in this time.
  2. Preheat oven to 350°F. Lightly grease a 9-by-13-inch metal pan.
  3. In the bowl of a stand mixer fitted with the paddle attachment, beat together sugar, oil, vanilla, salt, baking soda, and cocoa powder until combined.
  4. Add eggs one at a time, beating well after each addition.
  5. Add the wet chocolate mixture to the starter mixture, and stir until smooth. Pour batter into prepared pan.
  6. Bake for 30-40 minutes, until a cake tester inserted into the center comes out clean.
  7. Remove from oven. Set the pan on a cooling rack until completely cooled and ready to frost.

To Make the Frosting

  1. Add butter and peanut butter to a large bowl. Use a hand mixer to beat until creamy and well-combined. 
  2. Gradually add powdered sugar on low speed until combined. Scrape down the sides and bottom of the bowl as needed. 
  3. Stir in vanilla extract, salt, and milk until well-combined. Beat on high speed until fluffy, about 30 seconds to 1 minute.
  4. The mixture should be fluffy and creamy. If the frosting isn’t coming together and seems dry, add milk 1 teaspoon at a time, beating to incorporate after each addition. 
  5. Frost cooled cake in the pan.
  • Prep Time: 15 minutes
  • Cook Time: 40 minutes
  • Category: Cake
  • Method: Baking
  • Cuisine: Dessert

Keywords: sourdough, starter, cake, chocolate, peanut butter