Peanut Butter Sheet Cake with Marshmallow Frosting

Peanut butter lovers rejoice! This Peanut Butter Cake with Marshmallow Frosting is the dessert recipe of your dreams. A moist cake that’s full of peanut butter flavor- everyone needs a good sheet cake recipe box.

angle of slice of peanut cake with peanut topping


This Peanut Butter Cake is a great cake all on its own. Moist and full of peanut buttery (is that a word?) flavor, it will be sure to please everyone at your party or gathering. Unless, of course, they have a peanut allergy, then keep this bad boy far away from them!

It is also super easy to make, as it is a sheet cake versus a traditional peanut butter layer cake. We all know I am far from a great baker. LOL.

Peanut Butter Cake Ingredients

The cake itself is made from peanut butter and your usual cake mix ingredients. Most of them I’m sure you’ll be able to find right in your pantry.

overhead of peanut butter sheet cake with marshmallow frosting

Dry ingredients:

  • all-purpose flour
  • white sugar
  • brown sugar
  • baking soda
  • baking powder
  • fine sea salt

Wet ingredients:

  • creamy peanut butter – I do not recommend using chunky peanut butter if you like a smooth cake. Of course, if you’d like a bit of added crunch, feel free to use it. Also I’m not a fan of using natural peanut butter for this cake. It’s generally not as sweet as say Jif or Skippy.
  • milk 
  • vanilla extract
  • eggs 
  • vegetable oil  

Peanut Butter Frosting Recipe

For my Peanut Butter Cake, I opted for an equally as delicious frosting: easy marshmallow frosting! I can see the peanut butter fans out there swooning while reading this cause yes, you are totally allowed to make just the frosting and eat it with a spoon. We won’t judge.

spatula picking up a slice of peanut butter cake

But hey, this is a lot of work, albeit pretty simple, for frosting, so if you don’t want to mess with it, sub in a tub of chocolate frosting, Chocolate Buttercream or even cream cheese frosting.

But I do have to tell you, the combination of peanut butter and marshmallow is out of this world and totally worth the extra time and effort. Plus, this frosting would also taste great on a chocolate mayonnaise cake too!

Marshmallow frosting ingredients:

  • white sugar
  • evaporated milk
  • butter
  • creamy peanut butter
  • mini marshmallows
  • vanilla extract

Peanut Butter Cake Recipe

Are you ready to start making the best peanut butter cake ever?

  1. Preheat your oven and prep a 9×13 inch pan with cooking spray, set aside.
  2. In a large mixing bowl, cream peanut butter and sugar until light and fluffy- this does take a while, some folks skip this step and it is super important. Make sure to scrape the sides and bottom of the bowl and then add in the wet ingredients.
  3. Sift the dry ingredients before adding to the peanut butter mixture, this ensures they are well mixed without having to overmix the batter and potentially land a dry cake. Mix until there are just no dry spots remaining.
  4. Pour batter into the prepared pan and bake until it passes the toothpick test.
spreading cake batter into a pan
bite of cake removed from slice of cake

Top It

Usually you would wait until a cake is cooled to room temperature before you frost it. However with this ultimate peanut butter cake you do just the opposite. I’ve found that the best thing to do is to pour the hot frosting right on top of the hot cake and gets all gooey.

No fancy offset spatula or disposable piping bag needed for this delicious cake, just simply pour over the frosting and dress is up with whichever toppings you’d like.

close up of frosting dripping off of cake

No matter which way you dress it up, or don’t, grab a cold glass of milk and enjoy your sweet treat!

Our favorites include:

  • Honey roasted peanuts
  • Chopped Reeses Peanut Butter Cups
  • Melted chocolate
  • Chocolate chips or peanut butter chips
  • Chocolate ganache
  • Plain- the cake and the frosting are that good that you don’t need much more!
angle of frosted sheet pan cake

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Instant Pot Peanut Butter Cheesecake

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close up slice of peanut butter cake with hot frosting
slice of peanut butter cake with frosting

Peanut Butter Cake with Marshmallow Frosting

4.91 from 11 votes
Peanut Butter Cake with Peanut Butter Marshmallow Frosting and honey roasted peanuts is an easy cake recipe that is moist and perfect for any occasion.
Prep Time: 20 minutes
Cook Time: 30 minutes
Cooling Time: 1 hour
Total Time: 1 hour 50 minutes
Servings: 16 slices


Marshmallow Frosting:


  • 1/4 cup honey roasted peanuts coarsely chopped


  • Preheat your oven to 350°F. and prepare a 9×13 baking pan by spraying generously with non-stick spray and set aside.
  • In the bowl of a stand mixer equipped with a paddle attachment, cream the peanut butter and both sugars until light and fluffy.
    bowl of peanut butter cake batter in a bowl
  • Scrape the sides and bottom of the bowl and ad in the milk, vanilla, eggs, and oil, and mix until well combined.
  • Sift in the flour, baking soda, baking powder, and salt and mix until there are no dry spots remaining.
  • Pour the cake batter into the prepared pan and bake for 25-30 minutes or until a toothpick inserted in the center of the cake comes out clean. Remove from the oven and frost immediately.
    spreading cake batter into a baking dish


  • About 5 minutes before the cake is scheduled to be removed from the oven start to make the frosting.
  • In a medium saucepan, combine the sugar, evaporated milk and butter and heat over medium-high, stirring continuously.
  • When sugar is dissolved, add the peanut butter, marshmallows and vanilla. Stir until smooth and fully incorporated over very low heat.
  • Pour warm frosting mixture over the hot Peanut Butter Cake and spread around to cover fully. Sprinkle with honey roasted peanuts immediately while frosting is still tacky.
    peanut butter frosting on cake
  • Allow to cool completely before serving.
  • If you’ve tried this recipe, come back and let us know how it was in the comments or ratings.


Calories: 435 kcal, Carbohydrates: 59 g, Protein: 11 g, Fat: 19 g, Saturated Fat: 6 g, Polyunsaturated Fat: 4 g, Monounsaturated Fat: 7 g, Trans Fat: 1 g, Cholesterol: 26 mg, Sodium: 291 mg, Potassium: 317 mg, Fiber: 2 g, Sugar: 39 g, Vitamin A: 95 IU, Vitamin C: 1 mg, Calcium: 77 mg, Iron: 2 mg
Author: Jessica Formicola
Calories: 435
Course: Dessert
Cuisine: American
Keyword: marshmallow frosting, peanut butter cake, sheet cake
Did you make this recipe?I’d love to see your recipes – snap a picture and mention @savoryexperiments or tag #savoryexperiments!
peanut butter cake for pinterest
frosting dripping off of cake slices
Jessica Formicola in her ktichen

About the Author

Jessica Formicola

Jessica the mom, wife and chef behind Savory Experiments. You might see her on the Emmy- nominated TV show Plate It! or on bookshelves as a cookbook author. Jessica is a Le Cordon Bleu certified recipe developer and regularly contributed to Parade, Better Homes & Gardens, The Daily Meal and more!

Read More About Jessica

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Recipe Rating

Questions and Reviews

  1. 5 stars
    My kids are peanut butter fanatics and absolutely loved this cake! Definitely going into the dessert rotation.

  2. 5 stars
    This cake looks amazing and so delicious! My family is going to be all over this. Can’t wait to make this with my daughter!

  3. 5 stars
    This is such a delicious cake and the frosting is out of this world! My kids absolutely love this.

  4. 5 stars
    Just made this for my sons birthday he absolutely loved it, actually he didn’t want to share any and keep it all to himself it was so delicious!

  5. G’day and definitely different!
    Thanks for sharing!
    Cheers! Joanne
    Viewed as part of the Foodie Friends Friday

  6. Jess- how wonderful the Peanut Butter Cookie Dough Squares are! Made them for the Annual Camp Dinner and everyone raved about the taste. I told them all I found the recipe on “Savory Experiments”. (I tell everyone about your site)Joni

  7. 5 stars
    I have been looking for a new dessert with peanut butter. I believe I just found one. I too like the “dough” taste, so I’m sure this will be a hit with me! *LOOKS HEAVENLY* Maybe the next dessert for camp dinner. Joni