This delicious Peanut Butter Cake with Dark Chocolate Icing Recipe is the perfect dessert for serving a crowd, and it is so very easy to make.

peanut butter sheet cake

Peanut Butter Cake with Dark Chocolate Icing Recipe

This Peanut Butter Cake with Dark Chocolate Icing Recipe may look a little unassuming, but don’t let it fool you. It’s one amazing decadent dessert! Crazy good is what it is. Randy said it was like crack cake (Mom, that means he couldn’t stop eating it. We don’t do drugs). And he has a pretty picky palate to please when it comes to desserts. Crack cake. Yep. It’s kinda like that.

Other than the incredible flavors of this cake, with the always pleasing combinations of peanut butter and dark chocolate, this sheet cake recipe couldn’t be easier. No mixers (except for a spoon plus your hands) are needed. This cake and frosting can be made and ready to devour in under an hour. And it will be devoured so make sure you have some other people around to eat it or you won’t be able to control yourself. I’m just guessing that this may happen … just guessing. It is the perfect dessert to serve for a crowd. No fuss. Serve from the pan. Easy peasy. You’ll have a happy crowd, I promise.

A side note, another fabulous peanut butter and chocolate recipe you will truly enjoy is this Chocolate Peanut Butter Cheesecake Bars Recipe.

peanut butter sheet cake recipechocolate and peanut butter cakepeanut butter cake with chocolate frosting

Peanut Butter Sheet Cake recipe notes:

  • If you are out of buttermilk, substitute by adding 1 tablespoon of lemon juice to 1 cup of milk or heavy cream, whisk together and allow it to sit for about 5-10 to thicken and curdle.
  • This cake is made using an 18×13” jelly-roll pan. They are easy to find at big box stores in sets of 2 or 4. I use them for everything. Really. They are used all the time.
  • This Dark Chocolate Frosting recipe includes espresso powder. It really deepens and intensifies the chocolate flavor in a wonderful way. Coffee granules can be used as well but if you can find espresso powder, buy some. It’s a great addition to chocolate cakes, cookies, pancakes, and muffins too.

chocolate and peanut butter cake

Peanut Butter Cake with Dark Chocolate Icing Recipe

Yield: 24
Prep Time: 25 minutes
Cook Time: 30 minutes
Total Time: 55 minutes

An incredibly easy and decadent peanut butter sheet cake that is great for serving a crowd, topped with an easy icing that is made stovetop in just a few minutes. Perfect for topping sheet cakes!


For the Peanut Butter Cake:

  • 6 ounces butter, salted (1 1/2 sticks)
  • 1/2 cup smooth peanut butter
  • 1 cup boiling water
  • 2 cups flour
  • 1/2 teaspoon baking soda
  • 1/4 teaspoon salt
  • 2 eggs
  • 1/2 cup buttermilk
  • 2 teaspoons vanilla
  • 2 cups brown sugar, packed

For the Dark Chocolate Icing:

  • 1 1/2 stick butter
  • 5 tablespoons milk
  • 4 tablespoons unsweetened dark cocoa powder (substitute regular cocoa powder if needed)
  • 1/2 teaspoon instant espresso powder or coffee granules
  • 2 cups powdered sugar
  • 1 teaspoon vanilla extract


  1. For the Peanut Butter Cake: Preheat oven to 350-degrees F. Butter and flour (or coat with baking spray) a 18x13-inch jelly-roll pan/baking sheet.
  2. Melt butter in a small saucepan. Whisk in peanut butter until smooth. Gradually stream in boiling water whisking until combined. Remove from heat and let sit for at least 2 minutes.
  3. Meanwhile, whisk together flour, baking soda, and salt. Set aside.
  4. In a separate large mixing bowl, beat together eggs, buttermilk and vanilla. Whisk in sugar to combine.
  5. Slowly stream in warm butter/peanut butter mixture into the egg/buttermilk mixture, whisk to combine.
  6. Gradually stir in flour mixture and whisk to combined.
  7. Pour batter into prepared pan and bake in a 350-degree F oven for 20-25 minutes or until done.
  8. For the Dark Chocolate Icing: Add butter, milk, cocoa powder and espresso/coffee powder to a medium saucepan over low heat, allow butter to totally melt, whisk occasionally until combined and smooth. Remove from heat, gradually add in powdered sugar and vanilla, whisking until smooth. Pour warm frosting over cake, spread evenly to cover cake until smooth. Cut and serve.

Did you make this recipe?

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Originally published August 30, 2014.