Peanut Butter S’mores Cake

Aug 13

Peanut Butter S’mores Cake.

Chocolate cake layers baked on graham cracker crust, filled with chocolate ganache, peanut butter frosting and marshmallow cream.

Some people don’t think my sister and I look much alike. She has more traits of my mom’s side and I have more traits of my dad’s side. But let me assure you, we are blood and proof is in the sweet tooth.

Case in point, I asked her what kind of cake she wanted for her birthday, and without hesitation, she said to me, “peanut butter s’mores.” Not just a s’mores cake. Not just a regular peanut butter cake. A peanut butter s’mores cake! It was pure genius. This is literally the kind of cake I dream about! (I’ll admit now, I’m a little biased toward this cake because I love peanut butter. Hmm, love might be talking about my relationship with peanut butter too lightly. I’m obsessed with the stuff. It’s a main food group in my diet. I’ll add it to just about any other food. Don’t judge.) Anyway, with that secret out, I’ll just say I was so excited to make this cake, and eat it with my sister! I knew we would both appreciate and savor every bite together!

To make this wildly rich and delicious cake, I looked up several different recipes and ultimately decided to piece together my own creation in order to get what I was looking for. You’ll see I’ve used my go-to dark chocolate cake for the base. Its bittersweet flavor balances nicely with the more savory flavor of the peanut butter filling and the sweetness of the marshmallow frosting. And I love the baked in graham cracker layer! It adds a little contrast in texture to the rest of the cake. 

Oh, it’s just so good… and like I said, seriously rich!

Also, I know this looks like a lot of steps, but don’t let that scare you off from making this cake. When I’m making a cake with several steps like this, I spread out the baking over a few days. With this cake, I made the cakes a few days before the party and froze them until I was ready to assemble. Next, I made the peanut butter filling and ganache a day ahead. You can store the peanut butter filling and ganache in an air-tight container at room temperature for a day, or in the refrigerator for a few days. If you decide to stick them in the fridge, let both get to room temperature before you spread them on the cake during assembly. Finally, I made the marshmallow frosting day of and frosted the cake right away when it was finished.

Peanut Butter S'mores Cake

Yield One 3-layer, 8-inch cake

Peanut Butter S'mores Cake.

Chocolate cake layers baked on graham cracker crust, filled with chocolate ganache, peanut butter frosting and marshmallow cream.


For the Graham Cracker Crust

  • 3 cups (360 g) graham cracker crumbs, about 25-27 rectangular crackers (this is best done in a food processor or blender, but can be done by placing the graham crackers in a zip-lock bag and rolling over the crackers with a rolling pin)
  • 3/4 cup (169.5 g) unsalted butter, melted
  • 1/2 cup(100 g)  granulated sugar 


  • 1 3/4 cups, plus 2 tablespoons (225 g) all-purpose flour
  • 2 cups, minus 2 tablespoons  (375 g) granulated sugar
  • 3/4 cups (88.5 g) dark cocoa powder
  • 2 teaspoons (8 g) baking soda
  • 3/4 teaspoon (3 g) baking powder
  • 1 teaspoon (5.6 g) kosher salt
  • 1 cup (240 g) buttermilk, at room temperature
  • 1/2 cup (109 g) vegetable oil
  • 3 large eggs, at room temperature
  • 1 teaspoon (4.2 g) pure vanilla extract
  • 1 cup (236 g)  hot water 

For the Peanut Butter Filling (used in Magnolia Bakery's Peanut Butter Pie)

  • 1 cups ( 231 g) heavy cream
  • 1 1/2 cups (337.5 g) cream cheese
  • 3/4 cups (187.5 g) peanut butter
  • 1/2 cup (62.5 g) confectioners' sugar (more if you want it on the sweeter side)
  • 1/2 tablespoon (2.1 g) pure vanilla extract

For the Chocolate Ganache

  • 1 cup (231 g) heavy cream
  • 8 ounces (228 g) bittersweet chocolate, chopped or pieces

For Marshmallow Frosting (from

  • 3 egg whites, room temperature
  • 1/4 (1.4 g)  teaspoon salt
  • 1/3 cup (66.6g) sugar
  • 1 cup (328 g) karo syrup
  • 2 tablespoons (29.5 g) water
  • 1 tablespoon (4.2 g) vanilla bean paste or clear vanilla extract



  1. Preheat your oven to 375 degrees F. Spray three 8-inch or four 6-inch round cake pans with non-stick spray and then line with parchment. Spray again. Set aside.
  2. In a medium sized bowl combine the graham cracker crumbs, melted butter and sugar. Stir until all the graham cracker crumbs are damped by the melted butter.
  3. Divide evenly between the three pans and press down firmly with your hand or the back of a spoon.
  4. Bake for 8-10 minutes, until golden brown. Let cool while you make the chocolate cake batter. 


  1. Preheat the oven to 360 degrees F.
  2. Combine the flour, sugar, cocoa, baking soda, baking powder, and salt into the bowl of an electric mixer fitted with a paddle attachment and mix on low speed until combined.
  3. In another bowl, combine the buttermilk, oil, eggs, water and vanilla.
  4. With the mixer on low speed, slowly add the wet ingredients to the dry, scraping the bottom of the bowl with a rubber spatula.
  5. Pour the batter into the prepared pans (about 15 ounces in each pan), over the cooked graham cracker crusts and bake for 18-20 minutes, until a toothpick inserted in the center of the cake comes out almost clean.
  6. Cool in the pans for 10 minutes, then turn them out onto a cooling rack and cool completely.
  7. Wrap in plastic wrap and chill until ready to use. 

For Chocolate Ganache

  1. In a small pot, bring the cream to a simmer. Pour the cream over the chocolate pieces and let sit about 5 minutes.
  2. Whisk the ganache until smooth and shiny. Set Aside. (Can stick it in the fridge to let it harden a thicken up a little. Don't use it while warm or it will melt the peanut butter filling.)

For the Peanut Butter Filling

  1. In a medium bowl, beat the cream cheese with the paddle attachment on medium-high until smooth and creamy. 
  2. Lower mixer speed to medium and add the peanut butter, sugar, and vanilla. 
  3. Gently fold the whipped cream into the cream cheese mixture until completely combined. Set aside.

For the Marshmallow Frosting

  1. In the bowl of a standing mixer, whisk the eggs and salt until fluffy and frothy.
  2. Meanwhile, heat the sugar, corn syrup, water and vanilla paste. Heat over medium flame until the sugar is dissolved and just simmering, about 5 minutes.
  3. With the mixer on medium speed, add a tiny bit of the hot sugar mixture to the egg whites at a time. (Temper the eggs - don't scramble the them)
  4. Eventually, all of the sugar will be added and then turn the mixer up to high. Beat the mixture on high for about 5 minutes or until very stiff and shiny.


  1. Place one chocolate cake and graham cracker cake round on your cake stand, with the graham cracker side facing up.
  2. Spread half of your ganache on the graham cracker layer, followed by half of your peanut butter filling.
  3. Place the second chocolate and graham cracker cake on top, with the graham cracker layer facing up. Repeat step two.
  4. Place final cake layer, face down, on top of the peanut butter filling. Dollop the marshmallow frosting on top. I used the back of my spoon to swirl the frosting and create a textured look.
  5. Carefully use a kitchen torch to brown some areas of the frosting.

3 thoughts on “Peanut Butter S’mores Cake

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  1. I’m curious if not baking off the graham cracker crust was intentional in this recipe versus the other cakes with a graham cracker crust? I questioned why that step wasn’t in this recipe, but ultimately decided to follow the recipe as written and the crust fell apart when I took the cakes out of the pan. Darn it! So, I would recommend to anybody making this recipe, just follow the cake recipe for the Ultimate S’more cake and then use these fillings because that peanut butter filling is to die for.

  2. Hi Courtney, This cake looks great. I’m making it now. But I’m a little confused about the peanut butter filling. Is the heavy cream whipped before adding it to the peanut butter and cream cheese mixture? This seems unclear to me in your recipe. Thanks for your help. Everything looks good so far (though the chocolate cake raised into quite a dome that I will be cutting down).