Peanut Butter S’mores Cake – graham cracker cake layers with whipped peanut butter buttercream, toasted marshmallow filling, toasted graham crackers and chocolate ganache.

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!

The 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 Make 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 3/4 cup heavy cream for 1 cup of your chips. You may need to add an extra 1/4 cup cream to make it a little thinner.
- For any other type of baking chip, you’ll only need 1/4 to 1/3 cup heavy cream for 1 cup of the chips.
1 cup dark chocolate + 3/4 cup to 1 cup heavy cream When using a drip in between cake layers, make sure it’s completely room temp. 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 1/4 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 1/2 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.

Enjoy!

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.