The most delicious s'mores cake ever!! This cake is really bringing the campfire treat to your dinner table. Moist chocolate cake layers are baked on a buttery graham cracker crust. The filling between each cake layer consists of a smooth chocolate ganache and a toasted marshmallow whipped cream. Every cake needs a frosting, and this one is happens to include graham cracker crumbs and toasted marshmallows in the frosting. Yep! A graham cracker toasted marshmallow buttercream frosting. You'll take a bite of this cake and know immediately, it's a S'MORES CAKE!
Preheat the oven to 325°F. Spray three 8-inch round cake pans with nonstick cooking spray. Line the bottoms with parchment paper.
To a large bowl add the graham cracker crumbs, melted butter, sugar, and salt. Mix to combine.
Press 1/3 of the graham cracker mixture into each cake pan. Firmly pressing to create a crust at the bottom of the pan. Bake for 4 minutes. Remove and let cool while preparing the cake batter.
Chocolate Cake
In a medium bowl, whisk the flour, sugar, cocoa, baking soda, baking powder, and salt.
In the bowl of a stand mixer fitted with a paddle attachment mix the eggs, buttermilk, vegetable oil, and vanilla until combined.
Add the dry ingredients to the stand mixer and mix until combined. Pour in the hot water and mix on medium speed until combined.
Divide batter evenly between the cake pans (pouring directly on top of the crusts) and bake for 23-27 minutes or until a toothpick comes out with a few moist crumbs but no wet batter.
Remove cakes from the oven and allow to cool for 10 minutes. Remove from the cake pans and allow cakes to cool on a cooling rack until completely cool.
Chocolate Ganache
Heat the cream in the microwave until hot and pour over the chocolate chips. Let sit for 2 minutes, then stir until smooth. You will use this for the filling between the cake layers, and the remaining ganache will be used for a drip around the exterior of the cake once frosted.
You may need to add a tablespoon or two of cream to get the ganache to a good drip consistency. When ready to add to the outside of the cake, I like to do a test drip on a glass cup to make sure it will drip down enough but not too much.
Toasted Marshmallow Whipped Cream
Toast the marshmallows by placing the marshmallows on a cookie sheet that has been sprayed with nonstick spray.
Turn oven to broil and put the cookie sheet of marshmallows in the oven. The marshmallows will get toasted really quickly (less than two minutes in my oven), so watch them closely!
In a heat-safe bowl, add the freshly toasted marshmallows and 2 teaspoons of heavy cream and mix until the mixture is smooth. Set aside.
In a separate bowl, beat the heavy cream until stiff peaks form.
Gently fold the marshmallow mixture into the whipped cream and store in the refrigerator until ready to use.
Toasted Marshmallow Graham Cracker Buttercream
Toast the marshmallows by placing the marshmallows on a cookie sheet that has been sprayed with nonstick spray.
Turn oven to broil and put the cookie sheet of marshmallows in the oven. The marshmallows will get toasted really quickly (less than two minutes in my oven), so watch them closely! Set aside to cool slightly.
In the bowl of a stand mixer fitted with a paddle attachment, beat the butter until it’s light and very smooth.
Add the graham cracker crumbs, salt, and toasted marshmallows and beat until the mixture is homogenous.
Add the vanilla and slowly add the powdered sugar and heavy cream. Once all the ingredients have been added, beat the buttercream on high speed for 3 minutes. This can be made ahead of time and stored in the refrigerator. It will need to sit at room temperature for 4-5 hours after refrigeration to become soft and spreadable again.
Assembly
Place a cake layer, graham cracker crust down, onto a cake board and cover with a thin layer of buttercream.
Create a buttercream dam by piping a ring of buttercream around the top edge of the cake layer. Spread a layer of chocolate ganache across the bottom of the dam, and then fill the rest of the space with the toasted marshmallow whipped cream. Be sure to not overfill the cake as it will seep out when you add the next layer and make the cake unstable and difficult to finish icing.
Place the second cake layer on top of the buttercream ring, graham cracker crust side DOWN, cover with a thin layer of buttercream and repeat step 2.
Place the third cake layer on top and crumb coat the entire cake in a thin layer of buttercream. Refrigerate or freeze for 10-15 minutes, until the buttercream is cold and no longer soft.
Add the final layer of frosting around the entire cake.
Add the chocolate ganache drip and decorate as desired.
Notes
For information on storing and freezing cakes, including how to freeze cake layers, buttercream and decorated cakes, check out my How to Store and Freeze Cakes guide!