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The ultimate s'mores cake for peanut butter lovers! Graham cracker cake layers with a toasted marshmallow filling, toasted graham crackers, chocolate ganache and peanut butter buttercream.
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5 from 6 votes

Peanut Butter S'mores Cake

Graham cracker cake layers with toasted marshmallow filling, toasted graham crackers, chocolate ganache and peanut butter buttercream
Course: Dessert
Cuisine: Cake
Keyword: chocolate, graham cracker, Graham Cracker cake, marshmallow, Peanut Butter
Servings: 20 people



  • 3 cups (360 g) finely ground graham crackers 27 full rectangles
  • 3/4 cup (170 g) unsalted butter melted
  • 1/2 cup (100 g) granulated sugar


  • 1 cup (120 g) finely ground graham cracker crumbs 9 full rectangles
  • 2 cups (240 g) all-purpose flour
  • 1 3/4 tsps. (7 g) baking powder
  • 3/4 tsp. (3 g) baking soda
  • 1/2 tsp. (2 g) ground cinnamon
  • 3/4 tsp. (2.5 g) salt
  • 1 cup (226 g) unsalted butter at room temperature
  • 1 2/3 cups (270 g) granulated sugar
  • 4 large or extra large eggs at room temperature
  • 2 cups (480 g) buttermilk at room temperature


  • 24 marshmallows regular size
  • 1 cup (125 g) powdered sugar measured and then sifted
  • 1 cup (226 g) unsalted butter at room temperature
  • 1/2 tsp. (2 g) vanilla extract
  • 1 jar (200 g) marshmallow fluff


  • 1 cup (175 g) dark or semi-sweet chocolate chips
  • 3/4 to 1 cup (170 to 230 g) heavy whipping cream


  • 1 1/2 cups (339 g) unsalted butter slightly cold
  • 1 cup (240 g) creamy peanut butter I use Skippy
  • 5 cups (625 g) powdered sugar measured and then sifted
  • 1 tbsp. (13 g) vanilla extract
  • 1/4 cup (57 g) heavy whipping cream
  • Pinch of salt
  • *This buttercream recipe makes enough to fill and cover your cake. If you want to add additional piping, you’ll want to make an extra 1/2 batch.



  • Preheat your oven to 375 degrees F. Line a half sheet baking pan with parchment paper. Set aside.
  • In a food processor, combine the graham cracker, melted butter and sugar. Blend/mix until the mixture resembles wet sand.
  • Sprinkle the graham cracker crumbs onto the prepared parchment paper. Bake for 10 to 15 minutes.
  • Let cool completely before using in the cake. Can be made ahead of time and stored in the freezer in an airtight container.


  • Preheat your oven to 350 degrees F. Spray three 8-inch or four 6-inch round cake pans with non-stick spray and then line with parchment. Spray again.
  • Place the graham crackers in a food processor or blender and pulse until the cookies are finely ground and resemble flour.
  • In a medium-size bowl, combine the graham cracker crumbs, flour, baking powder, baking soda, cinnamon and salt. Whisk until the ingredients are well-blended. Set aside.
  • In the bowl of a stand mixer fitted the paddle attachment, beat the butter and sugar on medium speed until light and fluffy. Add the eggs, one at a time, beating well after each addition and making sure to scrape down the sides of the bowl between each addition.
  • With the mixer on low speed, add 1/3 of the dry ingredients and mix until combined. Slowly add half of the buttermilk and mix until incorporated. Continue alternating the flour and buttermilk until it has all been incorporated. Scrape down the sides of the bowl and slowly mix for another 20-30 seconds.
  • Divide the batter evenly among your pans and bake for about 25 to 30 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs on it. Cool 10 minutes on a wire rack before inverting onto cooling racks to cool completely. 


  • Place the marshmallows on a cookie sheet lined with parchment paper and sprayed with nonstick cooking spray. Place on the middle rack of the oven, and broil the marshmallows until golden brown on top, about 30-60 seconds. Keep your eye on them!
  • Remove the pan from the oven and gently turn the marshmallows over and broil them again until they are golden brown on the other side.
  • In the bowl of a stand mixer fitted with the paddle attachment, combine the butter and powdered sugar and beat on low until blended. Add the vanilla and mix on medium speed for about three minutes.
  • With the mixer on low speed, add the marshmallow cream and (cooled) toasted marshmallows, and mix for about one minute.
  • Can be made ahead of time and stored in an airtight container in the refrigerator.


  • In a microwave safe bowl, heat the cream for about one minute.
  • Pour the cream over the chocolate chips and let sit for a couple minutes. Stir until chocolate is melted. If needed, heat for another 30 seconds to melt the chocolate chips completely. Let cool to room temperature before using using in the cake.
  • Follow instructions above for making the mixture thinner for the outer drip.


  • In the bowl of electric mixer fitted with the paddle attachment, combine the butter and peanut butter. Beat on medium-high speed until smooth, about 2 to 3 minutes.
  • Add the powdered sugar to the bowl and mix in, slowly at first until incorporated, then increasing the mixer speed to high once all of the powdered sugar has been added. Blend in the vanilla extract, salt and heavy whipping cream, and continue to whip on high speed until very fluffy, about 4-5 minutes, scraping down the sides of the bowl as needed.
  • Stir by hand with a wooden spoon to push out air pockets.


  • Place the first cake layer on a cake board, bottom-side down. Pipe a rim of buttercream around the edge and fill with about 1 cup of the toasted marshmallow filling.
  • Sprinkle about 1/2-1 cup of the graham crackers on top and pat into place with your hand. Drizzle the chocolate drip on top, making sure to not let the chocolate go outside of the buttercream rim you piped.
  • Repeat these steps with the second cake layer.
  • Place the final cake layer, top side down, on the final layer of fillings. Apply a thin layer of buttercream over the entire cake. This is the crumb coat. Freeze the crumb coated cake for about 15 minutes.
  • Once the crumb coat is set, finish frosting the cake and apply the drip. Remember to refer to the tutorial above for tips for the drip.