Peanut Butter S’mores Cake – graham cracker cake layers with whipped peanut butter buttercream, toasted marshmallow filling, toasted graham crackers and chocolate ganache.
Table of contents
Decadent Peanut Butter S’mores Cake
Alright, peanut butter lovers! This cake is for you!
I made a Peanut Butter S’mores Cake YEARS ago for my sister’s birthday. It was basically my Ultimate S’mores Cake but with peanut butter buttercream instead of chocolate buttercream. It was delicious, but it wasn’t something that stood out on it’s own. I recently decided to rethink this cake and came up with a totally new version!
Graham Cracker Cake Layers
- The cake layers for this cake are my graham cracker cake layers from my Peanut Butter Graham Cake (another must-try if you love PB!). I love the hint of cinnamon these layers add to the cake.
- I then used the chocolate ganache/drip, toasted marshmallow filling and toasted graham crackers from my Ultimate S’mores Cake.
- And instead of chocolate buttercream, we’re using peanut butter!
So nothing is really new in this cake – just the combination of all these different elements. I think it’s so fun to play around with flavor combinations, and taking components from different cake recipes is the perfect way to try it out!
How to Cake It: The Perfect Drip
I know getting the perfect consistency for your drip can be tricky, so let’s talk about how to make the perfect drip!
Nail the cream to chocolate ratio
- For dark chocolate or semi-sweet chocolate, you’ll need more cream than any other type of baking chip. I recommend you start with ¾ cup heavy cream for 1 cup of your chips. You may need to add an extra ¼ cup cream to make it a little thinner.
- For any other type of baking chip, you’ll only need ¼ to ⅓ cup heavy cream for 1 cup of the chips.
1 cup dark chocolate + ¾ cup to 1 cup heavy cream When using a drip for the decoration on the outside of the cake, we’ll want to heat it up again for a few seconds to thin it out a bit. Hold the drip bottle at an angle so the drip falls off the cake like a waterfall. Pull back on the drip bottle in places you don’t want the drip to spill over the edge. Add a little of the drip on top of the cake and blend it in to the border.
How to melt the chocolate
- To melt your chips, I suggest heating your cream first and then pouring the hot cream over your chips. Let the cream sit for a minute on the chips and then stir to create a silky, smooth texture. If the chips don’t melt all the way at this point, microwave the mixture for 10 seconds and stir again.
- If you try to heat your chocolate and cream together in a microwave, you’ll likely seize the chocolate.
- An alternative to the microwave is a double boiler.
Making sure your consistency is perfect
- When I use the drip in between the cake layers, like you see above, I let the mixture get completely room temperature – for a couple reasons: 1.) the drip thickens as it cools, and 2.) I don’t want warm chocolate in between my layers melting buttercream.
- But when I’m ready to use the drip for the actual drip, I want it to be a little thinner and slightly warmer than what I used in between the layers. To do this, I usually heat that extra ¼ cup cream till it boils and then add it to what’s left of my room temperature drip that I used in between the layers.
How to Assemble the Peanut Butter S’mores Cake
Place your cake layer on a cake board or plate. Pipe a rim of frosting around the edge of the cake. 
Fill the center of the area with 1 cup of the toasted marshmallow filling. 
Sprinkle and then pat into place about ½ cup of the toasted graham crackers. 
Drizzle the cooled chocolate drip over the graham crackers. Place your second cake layer down, also top-side up. Repeat the steps for piping, filling, crumbs and drip. Remember to use drip that is room temperature and not warm. 
Place the final cake layer top-side down. Apply a thin layer of buttercream to act as your crumb coat.
- After you’ve chilled your crumb coated cake in the freezer for about 15 minutes, you’re ready to continue frosting your cake with the remaining buttercream and drip.
HOW TO MAKE BUTTERCREAM FROSTING
To get a light and fluffy homemade buttercream frosting, make sure you follow my tips over at: HOW TO MAKE THE BEST BUTTERCREAM
These steps are written up for my vanilla buttercream, but are supposed to be applied to any of my buttercream recipes.
- Sift your powdered sugar
- Use slightly cold butter
- Use heavy whipping cream
- Beat for 5 minutes
- Stir by hand
You’ll want to check out the post linked above for more details on each step.
Other Cakes You’ll Love
- Ultimate S’mores Cake
- Banana Nutella S’mores Cake
- Banana Peanut Butter Caramel Cake
- Peanut Butter Dream Cake
Peanut Butter S’mores Cake
Graham cracker cake layers with toasted marshmallow filling, toasted graham crackers, chocolate ganache and peanut butter buttercream
Ingredients
FOR THE GRAHAM CRACKER CRUMBS
- 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
FOR THE CAKE
- 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
FOR THE TOASTED MARSHMALLOW FILLING
- 24 marshmallows regular size
- 1 cup (125 g) powdered sugar measured and then sifted
- 1 cup (226 g) unsalted butter at room temperature
- ½ tsp. (2 g) vanilla extract
- 1 jar (200 g) marshmallow fluff
FOR THE CHOCOLATE GANACHE/DRIP
- 1 cup (175 g) dark or semi-sweet chocolate chips
- ¾ to 1 cup (170 to 230 g) heavy whipping cream
FOR THE PEANUT BUTTER BUTTERCREAM
- 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 ½ batch.
Instructions
FOR THE GRAHAM CRACKER CRUMBS
- 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.
FOR THE CAKE LAYERS
- 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 ⅓ 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.
FOR THE MARSHMALLOW FILLING
- 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.
FOR THE CHOCOLATE DRIP
- 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.
FOR THE BUTTERCREAM
- 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.
ASSEMBLY
- 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.
Does this freeze well? Or do the graham cracker crumbs go soggy?
It freezes really well. They won’t go soggy.
This cake was delicious!!! However, I was wondering why I had so much graham cracker crumb left over, was that just for extra decorating, did I miss something? I put it in between layers and some on top??? Also, after I baked the cakes they came out nice and puffed up, as the cooled they sank and made the cake really dense, and my layers seem thin…am I doing something wrong? I don’t seem to get a nice crumb, however they are very moist? Thank you!
If you have extra crumbs you can just add more to the middle next time! You might have overmixed your cake a little bit or your ingredients might have been old and that’s why it sank!
Amazing Recipe! I haven’t used a recipe on your website I haven’t loved. Thank you! Only feedback or tip for somebody trying this recipe is to cut the graham cracker crumb ingredients in half at least. I used as much as I could in the layers and as decoration and I threw away over 1/2 what a made. Which was sort of painful-butter isn’t cheap!
I made this cake for my cousin’s birthday this past weekend. She actually requested it back in March. Even though we couldn’t celebrate together, the cake was a big hit. The actual cake doesn’t seem overly sweet so the sweet filling and frosting aren’t too overpowering.
Love to hear it!
You say a jar of marshmallow fluff then you show a recipe for toasted marshmallows? Not sure where the fluff goes???
The marshmallow fluff goes in the marshmallow filling. It’s in the ingredients and directions.
Amazing! This is the first recipe of yours I’ve tried. My only suggestion is to change the wording of the ingredients for the cake…the first item listed is “1 cup (120 g) finely ground graham cracker crumbs 9 full rectangles.” I actually didn’t realize I was supposed to use the previously toasted graham cracker crumbs for this, until after I had baked the three layers and was rereading steps! I just used plain finely ground graham cracker crumbs. I’m redoing my layers now to get that toasty goodness in there. Perhaps no one else will make this error, but maybe consider changing that line to say 1 cup of the toasted graham + sugar + butter crumbs. 🙂 thanks again for sharing your wonderful recipes!
Ok, just read through again and now I think I was right the first time … using untoasted crumbs in the cake? Is that right?
You were right the first time. They are different graham cracker crumbs.
Can we omit marshmallow fluff from the recipe or is there any alternate?
You don’t have to do the filling if you don’t want.
Is the weight of the graham crackers (120g) as squares or as crumbs? I used already made graham crackers crumbs at that weight and the cake was so dense that it wasn’t very good. I’m wondering if that was the problem. Everything else was so good though! This peanut butter buttercream is my new go-to!
As squares.
This cake was delicious but the Graham cracker crumb recipe can be halved. You start off with 3 cups of Graham crackers plus butter and sugar but you only use a about 1-1.5 cup of crumbs during assembly. Soooo much leftover
You can half it next time! I always make sure I have extra to snack on 🙂