Extra soft & moist dark chocolate cake layers, fluffy vanilla bean toasted marshmallow filling, rich & silky chocolate ganache, the creamiest malted milk chocolate buttercream, and glossy salted bourbon toffee sauce come together to make this decadent 3-layer s’mores-inspired cake.
Before getting too immersed in Thanksgiving baking, we can’t forget about birthday cake season. It’s recognized year-round, of course, but especially the month of November. (Because everyone celebrates my birthday on November 8th, obviously.) For family and friends, the birthday cake requests tend to be pretty straightforward–“just chocolate” or “whatever’s easiest for you” or “the one that we had last time.” But when it comes to my birthday, I’m not settling for “just” anything. I want a unique, jaw-dropping flavor explosion… the kind of cake that makes your eyes widen and your face drool.
Thus, I present this luxurious twist on a s’mores cake: Three tall layers of the softest, moistest dark chocolate cake filled with fluffy vanilla bean toasted marshmallow cream and rich chocolate ganache, covered in silky malted milk chocolate buttercream and salted bourbon toffee sauce, adorned with pillowy toasted marshmallows. Like a s’more with the toasty marshmallow and smooth chocolate, but otherwise very very different. At the end of the day, this is a soft, melt-in-your-mouth chocolate cake with a beautiful marriage of flavors that evoke the essence of a s’more (not designed to taste like a graham cracker sandwich).
Dutch Chocolate Cake Layers
Let’s start with the deep, dark, extra moist, absurdly soft chocolate sponge. This is hands-down my favorite chocolate cake recipe and my go-to for all my chocolate layer cakes. What makes it special?
- Dutch cocoa ~ While cocoa is naturally acidic, Dutch cocoa is alkalinized, resulting in a smoother, deeper chocolatey flavor (think devil’s food cake). Look for any unsweetened cocoa “processed with alkali.” It may be called Dutch, black, or Ghirardelli’s “majestic” cocoa. We also use more cocoa in this cake compared to many other recipes for a rich dark chocolatey effect.
- Buttermilk and sour cream ~ This combo gives the cake full flavor, excellent rise, super soft texture, and incredible moisture. Full fat preferred for both.
- Neutral oil (such as refined almond oil, vegetable oil, or coconut oil) ~ Helps the cake retain even more moisture compared to butter.
- Espresso ~ Enhances the chocolate flavor of the cake (without making it taste like coffee).
- Baking soda and baking powder ~ Extra baking soda (sodium bicarb) is important for the optimal reaction with acidic buttermilk and sour cream and the fluffiest result.
Toasted Marshmallow Filling
It’s light, fluffy, and voluminous. Marshmallowy with a smooth mouthfeel–not overly sticky. Toasty and filled with pure vanilla bean flavor–not overly sweet.
Plus, you don’t have to make a meringue from scratch. With store-bought marshmallow cream (or “fluff”) and marshmallows, this doesn’t get any easier. The rundown:
- Butter and powdered sugar ~ Begin like you’re making a buttercream by mixing together softened butter and sifted powdered sugar.
- Marshmallow creme (or “fluff”) ~ This is your secret to create a fluffy, light, airy, stabilized filling that stands tall between the cake layers. It also creates a smooth consistency that tastes like marshmallow, but without all the chewiness. Here is an organic brand that tastes wonderful if you want to avoid artificial flavoring.
- Whole toasted marshmallows ~ Get the iconic toasty flavor of a s’more by adding toasted marshmallows right into the filling. Just broil them about 30-60 seconds on each side until golden brown all over. The heat also melts down the sugar, so after they cool, they blend in smoothly with the rest of the filling. Again, you can use an organic/natural brand like Whole Foods 365, Campfire, or Dandies to avoid artificial flavorings.
- Vanilla bean paste – A step above vanilla extract for bold, rich vanilla bean flavor. You will taste the difference!
Malted Milk Chocolate Buttercream
I am obsessed with this buttercream. It’s luscious, creamy, light, and it tastes like a chocolate malted milkshake. Although it’s made like an American buttercream (read: so easy), it’s not nearly as sweet or dense thanks to glossy chocolate ganache and relatively less powdered sugar. Simply blend:
- Unsalted butter ~ Softened to just cooler than room temperature.
- Powdered sugar ~ SIFTED. Just do it; I promise it makes a texture difference.
- Malted milk powder ~ The key to the special flavor of this malted milk chocolate buttercream
- Chocolate ganache ~ Made in under 5 minutes with semisweet chocolate chips and heavy cream. Cool to room temp before mixing in the frosting.
- Vanilla extract
Because this is a super silky, melt-in-your-mouth buttercream, I highly recommend chilling both the buttercream and cake layers before assembly to help stabilize the cake as you build it up. If the buttercream or cake is too soft, you run the risk of the cake sinking, leaning, or falling over.
Chocolate Ganache
Complete the melty s’more effect with a smooth layer of rich chocolate ganache in every bite. For this cake, I use a combination of semisweet and bittersweet chocolate to balance out the milky frosting and dark chocolate cake.
Pour hot heavy cream over a bowl of chocolate chips. Cover with foil and let it rest 3-5 minutes. Then gently stir until smooth. Bring it to room temp before assembling the cake.
Assembly Tips
- Chill the cake ~ Bake the cakes in advance so they have time to cool completely, then chill in the refrigerator or freezer for at least an hour or so. I often make the cake layers the night before, wrap them individually in plastic wrap, and store them in the fridge until ready to assemble. Cold cake is really important for structure while building the layers, because this cake is SOFT. At room temperature, it may start to come apart while frosting it.
- Chill the frosting ~ Similarly, the milk chocolate buttercream is soft and delicate, so firming it up in the refrigerator will help with structure while building the cake.
- Pipe a rim of buttercream ~ A tall wall of buttercream around the edges of the cake will hold the fillings in the center so the next cake layer can be placed on top without smashing the fillings out the sides. Within the rim of buttercream, spread on the room temperature chocolate ganache followed by the toasted marshmallow filling.
- Frost the top and sides of the cake with the rest of the chocolate buttercream. For a complete crumb coat followed by a thick coat of frosting, feel free to double the buttercream recipe. As written, it makes just enough to cover the cake.
- Chill the entire frosted cake before pouring over the salted toffee sauce. This will help slow the drip so it doesn’t all just run off the sides.
Salted Toffee Sauce
Finally, the golden magic. You can call this a butterscotch sauce or a toffee sauce. They’re both made with butter and brown sugar, and there’s no real difference in the sauce form. (If you were to continue cooking it to the final product, butterscotch would be cooked to a chew or soft crack, and toffee would be cooked longer to a brittle hard crack. Caramel, on the other hand, is made with white sugar rather than brown sugar.)
The hint of salt, nutty brown sugar, vanilla, and optional kick of bourbon together in a beautiful glossy sauce make the perfect enhancement for chocolate and toasted marshmallow. It also happens to be the easiest thing ever to make. Just add all the ingredients to a saucepan and simmer until thickened! I suggest making it in advance and storing it in a sealed container in the fridge until ready to use. Bring it to room temperature so the consistency is thick but just pourable.
This recipe makes a smaller 6-inch 3-layer cake. With the thick fillings to build it up, I’ve found this size to be more than enough for a party.
To convert this recipe into an 8-inch 3-layer cake:
- Dutch chocolate cake: Multiply the cake batter ingredients by 1.75 and divide between three 8-inch round cake pans. Be sure to weigh your ingredients to get the most accurate measurements. The cakes may take 1-3 minutes longer to bake.
- Fillings and frosting: Double the marshmallow filling, chocolate ganache, and chocolate buttercream.
- Toffee sauce: Multiply the toffee sauce by 1.5 if just using as a topping, or double for plenty to drizzle on each layer and over the top.
S'mores Cake with Malted Milk Chocolate Buttercream & Salted Toffee Sauce
Extra soft & moist dark chocolate cake layers, fluffy vanilla bean toasted marshmallow filling, rich & silky chocolate ganache, the creamiest malted milk chocolate buttercream, and glossy salted bourbon toffee sauce come together to make this decadent 3-layer s'mores-inspired cake.
Notes
This recipe makes a 3-layer 6-inch round cake.
The buttercream as written makes just enough to cover the top and sides of a 6-inch 3-layer cake. For a crumb coat plus thick coat of frosting or extra for decorating, double the buttercream recipe. You can also double the toffee sauce for enough to add in between the layers and over the top.
To convert this to a 3-layer 8-inch round cake:
- Mutiply the cake batter by 1.75: 1-3/4 cup sugar, 1/2 cup + 1.5 Tbsp oil, 7 Tbsp sour cream, 7 Tbsp buttermilk, 2 eggs, 1.5 tsp vanilla, 210g flour, 84g cocoa, 1-3/4 tsp baking soda, 7/8 tsp baking powder, 7/8 tsp sea salt, 7 fl oz boiling water, 7/8 tsp espresso powder.
- Lean toward the longer baking time (~21 min) for the cakes.
- Double the marshmallow filling, ganache, and buttercream.
- Multiply the toffee sauce by 1.5 (or double to add extra sauce in the center)
Ingredients
For the chocolate cake:
- 1 cup granulated sugar
- 1/3 cup neutral oil (such as refined almond oil, refined coconut oil, or vegetable oil)
- 1/4 cup full-fat sour cream, at room temperature
- 1/4 cup buttermilk, at room temperature
- 1 large egg, at room temperature
- 1 tsp vanilla extract
- 1 cup (120g) all-purpose flour, sifted
- 1/2 cup (48g) Dutch-process cocoa powder (unsweetened cocoa processed with alkali), sifted
- 1 tsp baking soda
- 1/2 tsp baking powder
- 1/2 tsp fine sea salt
- 1/2 cup boiling water
- 1/2 tsp instant espresso powder
For the malted milk chocolate buttercream:
- 2 Tbsp heavy cream
- 2.5 oz bittersweet or semisweet chocolate chips
- 1/2 cup unsalted butter
- 2 tsp malted milk powder
- 1.25 cups powdered sugar, measured then sifted
- 1/2 teaspoon vanilla extract
- Pinch salt
For the toasted marshmallow filling:
- 10 standard-size marshmallows
- 1/2 cup powdered sugar, sifted
- 6 Tbsp unsalted butter, softened to just cooler than room temperature
- 3.5 oz (1/2 package) store-bought marshmallow creme
- 1/2 tsp vanilla bean paste (or 1 tsp vanilla extract)
For the chocolate ganache filling:
- 3 oz semisweet or bittersweet chocolate chips
- 3.5 Tbsp heavy cream
For the toffee sauce (just enough to cover the cake):
- 2 Tbsp unsalted butter
- 1/4 cup dark brown sugar, packed
- 1/8 - 1/6 tsp fine sea salt, to taste
- 1/4 cup heavy cream
- 1/2 tsp vanilla extract
- 1/2 - 1 Tbsp bourbon (optional, to taste)
Instructions
Make the cake:
- Preheat the oven to 350°F. Spray 3 6-inch round cake pans with nonstick spray, line the bottoms with parchment paper, and spray again. Set aside.
- In a large mixing bowl or bowl of a stand mixer, whisk together the sugar, oil, sour cream, and buttermilk until smooth. Add the egg and vanilla and whisk until fully incorporated.
- Gradually mix in the sifted flour, cocoa powder, baking soda, baking powder, and salt. Whisk about 2 minutes by hand or with an electric mixer, occasionally scraping down the sides of the bowl, until thoroughly combined without lumps.
- In a microwave-safe measuring cup, microwave 1/2 cup water until boiling, then stir in the espresso to dissolve.
- While constantly stirring the batter, gradually mix in the hot coffee. Mix until smooth and even in consistency (making sure to scrape the sides and bottom).
- Divide batter into the 3 greased 6-inch cake pans. Bake for 19-20 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs.
- Remove the cakes from the oven and allow them to cool in the pan for 30 minutes. Then, remove the cakes from the pans and finish cooling on a wire rack to room temperature. Wrap the cakes in plastic wrap and chill in the fridge or freezer at least 1 hour before frosting.
Make the buttercream:
- Microwave cream in a microwave-safe measuring cup or bowl until nearly boiling (about 30 seconds, then in 10-second increments if needed). Pour the hot cream over the chocolate chips and cover with foil. Let sit about 4 minutes, then stir until smooth and no lumps of chocolate remain. Set aside to cool to room temperature.
- In the bowl of a stand mixer fitted with the paddle attachment or using an electric hand mixer, beat the butter 1-2 minutes on medium-high speed. On low speed, gradually mix in the powdered sugar and malt powder until combined. Add the vanilla and salt, and mix until combined. Then increase the speed to medium-high and beat for 3 minutes, until fluffy.
- Reduce the speed to low and add the cooled chocolate ganache. Mix until evenly combined. Scrape down the sides and bottom of the bowl with a rubber spatula and beat for 1-2 more minute on medium, until fluffy. If the frosting is too soft, place the bowl in the refrigerator for a few minutes to firm up, then finish mixing.
- With a wooden spoon or a rubber spatula, beat by hand to mix out any air pockets.
- Cover and chill in the refrigerator until ready to use.
Make the marshmallow filling:
- Turn the oven on high broil. Place the marshmallows on a baking sheet lined with parchment paper. On the middle oven rack, broil until the marshmallows are golden brown on top, about 30-60 seconds. Watch closely so they don’t burn. Remove the pan from the oven, turn the marshmallows over, and broil on the other side another 30-60 seconds, until golden brown.
- In the bowl of a stand mixer fitted with the paddle attachment or large mixing bowl with a handheld electric mixer, beat the butter about 1 minute. Gradually add in the powdered sugar and beat on low until blended. Add the vanilla bean paste and mix on medium speed 2-3 minutes. Scrape down the sides and bottom of the bowl.
- Add the marshmallow creme and mix on low speed until incorporated.
- When the toasted marshmallows are completely cool, mix them in on low speed. Scrape down the sides and bottom of the bowl, then increase the speed to medium and beat about 2-3 minutes longer.
Make the ganache filling:
- Microwave cream in a microwave-safe measuring cup or bowl until nearly boiling (about 30 seconds, then in 10-second increments if needed). Pour the hot cream over the chocolate chips and cover with foil. Let sit about 4 minutes, then stir until smooth and no lumps of chocolate remain. Set aside to cool to room temperature.
Make the toffee sauce:
- Melt the butter in a medium saucepan over medium heat. Add the brown sugar, heavy cream, and salt. Stir the mixture with a rubber spatula until fully blended. Bring the mixture to a boil and boil for 5-6 minutes, occasionally scraping down the sides of the pan.
- Remove the sauce from the heat, then stir in the vanilla and bourbon. (It should still be liquidy). Transfer to a heat-proof container to cool to room temperature. (It will thicken as it cools.)
- If not using immediately, store covered in the refrigerator. Bring to room temperature and stir when ready to use. The consistency should be thick but just pourable.
Assemble:
- Remove the chilled cakes from the refrigerator or freezer and unwrap. Remove parchment from the bottom. If needed, use a large serrated knife to even the tops of the cakes. Place the bottom cake layer on a cake board.
- Pipe a tall ring of chilled buttercream around the edge of the cake. It should be tall enough to hold up the second cake layer over the fillings in between.
- Spoon half of the room-temp ganache inside the ring of buttercream and smooth with the back of a spoon. Then dollop half of the marshmallow filling evenly over the ganache.
- Place the second cake layer on top and repeat with a rim of buttercream and fillings. Place the third layer on top.
- Use an offset spatula to cover the top and sides of the cake in the remaining buttercream. (If desired, double the buttercream recipe and frost a crumb coat plus a second thick layer of buttercream.) Chill the frosted cake in the refrigerator about 30 minutes.
- When the cake is cool, make the toffee sauce drip. The toffee sauce should be room temp, thick, and just pourable. Slowly spoon toffee sauce around the edges of the frosted cake, letting some drip down the sides. Then fill in the top of the cake with the remaining toffee sauce.
- The finished cake cake be stored in an air-tight container at room temperature 2-3 days, refrigerated about 5 days, or wrapped as individual slices in plastic wrap and frozen up to 3 months.