Mary Berg's Peanut Butter Chocolate Cake with Cornflake Crunch

Posted by Donna-Marie Pye on

A happy accident while grocery shopping led to the surprise star of this cake. While perusing the baking aisle looking for peanut butter chips, I hastily grabbed a bag of butterscotch instead. Typically, I find butterscotch chips cloyingly sweet but, with the cornflakes, peanuts, and extra sprinkle of salt, oh my gosh, so good. While either will work, this is just further proof of my belief that there are no mistakes in the kitchen. - Mary Berg




  • 1 cup all-purpose flour
  • ½ cup cocoa powder
  • 1 cup sugar
  • 1 tsp baking soda
  • ½ tsp baking powder
  • ½ tsp kosher salt
  • ½ cup buttermilk
  • ¼ cup canola oil
  • 1 egg
  • 1 tsp vanilla extract
  • ½ cup hot black coffee
  • ½ cup smooth peanut butter, not natural
Cornflake Crunch:
  • ½ cup butterscotch or peanut butter chips
  • 1 cup cornflakes
  • ¼ cup roasted peanuts, coarsely chopped
  • ¼ tsp flaky sea salt

Peanut Butter Ganache:

  • ¼ cup (35%) whipping cream
  • 4 oz milk chocolate, finely chopped
  • 2 tbsp smooth peanut butter, not natural


  1. Cake: Preheat your oven to 350°F and grease a 9-inch round cake pan with nonstick cooking spray.
  2. Sift the flour and cocoa powder into a large bowl. Whisk in the sugar, baking soda, baking powder, and salt until well combined. Add the buttermilk, oil, egg, and vanilla and whisk just to combine. Stir in the hot coffee and pour the batter into the prepared cake pan.
  3. Heat the peanut butter in the microwave or over a double boiler until thin and liquid, drizzle over the cake batter, and swirl in with a butter knife.
  4. Bake the cake for 30 to 35 minutes or until springy to the touch and a skewer inserted into the center comes out clean. Allow the cake to cool in the pan for 20 minutes then turn out onto a wire rack to cool completely.
  5. Cornflake Crunch: Meanwhile, make the cornflake crunch by melting the butterscotch or peanut butter chips in a large bowl in the microwave in 15-second bursts or by heating them over a double boiler. Stir in the cornflakes and peanuts and transfer to a piece of parchment, spreading the mixture into a clumpy but even layer. Sprinkle the top with the flaky sea salt and set aside to harden.
  6. Peanut Butter Ganache: Heat the whipping cream in the microwave or in a pan over low heat until steamy but not yet simmering. Add the chopped chocolate to a bowl, pour the hot cream overtop, and set aside for 5 to 10 minutes to melt the chocolate.
  7. Whisk the mixture until well combined, then whisk in the peanut butter until smooth. Allow the ganache to cool slightly until it is a thick, pourable consistency.
  8. Place the cake on a pedestal or serving plate and pour the ganache overtop, allowing it to drip down the sides. Break up the cornflake crunch and scatter overtop as well. The cake can be served immediately or stored covered at room temperature for up to 3 days.

Excerpted from In Mary’s Kitchen by Mary Berg. Copyright © 2023 Mary Berg. Photographs by Lauren Vandenbrook. Published by Appetite by Random House®, a division of Penguin Random House Canada Limited. Reproduced by arrangement with the Publisher. All rights reserved. 


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