S’mores Cake

This s’mores cake is my dream summer cake! We have all the components of a classic s’more in the form of a homemade meringue topping that tastes like toasted marshmallows, moist chocolate cake and a buttery graham crunch.

This cake was actually inspired by a huge container of egg whites leftover from an event and my love for rectangular cakes (and torching meringue). To me, this is the perfect birthday cake to make for a summer birthday.

The combination of moist chocolate cake, marshmallow meringue (no gelatin needed) and graham crumbs is an eternal crowd pleaser. Truly one of my favorite cakes I’ve made recently!

How I developed this recipe

This cake is made up of four components: a chocolate cake, graham crunch, marshmallow meringue and marshmallow buttercream. This cake is pretty much a mash up of some of my favorite baking components.

• Chocolate cake: No need to reinvent the wheel–I used the winning Ina Garten recipe from the chocolate cake bake off and baked the entire recipe in a 9×13. This slab of cake gets cut into four relatively thin layers of chocolate cake for my ideal cake to frosting ratio. The only change I made from the original recipe is to use 3 large egg yolks instead of 2 extra-large eggs. That way, we can use the egg whites to make the marshmallow meringue without having leftover yolks.
• Graham crunch: My friend Josh who owns a popular ice cream shop in Houston (Underground Creamery) introduced me to this recipe years ago. It’s simply graham cracker crumbs, butter, sugar and salt that gets baked into a graham cracker crumble (you can also find it in these s’mores shortbread). It’s a little more effort than just crushing up graham crackers for the filling, but these crumbs will hold their crunch for days even after being mixed with frosting. And they only take 7 minutes to bake!
• Marshmallow frosting: For the final coating of the cake, we’re using a marshmallow meringue instead of a more typical buttercream. I’ve compared a number of recipes online, and they all use about the same ratio of egg whites to sugar to make the meringue or what is essentially homemade marshmallow fluff. Don’t be tempted to skimp on the sugar–this is what gives the meringue its volume and body. The cream of tartar is also important to help stabilize the egg whites so it can hold up to toasting and sitting out once assembled.
• Marshmallow buttercream: I originally tried assembling this cake using only meringue in between the layers. Unfortunately, pure marshmallow filling (I.e. meringue) is just too soft–you need a sturdier layer of frosting to glue everything together. So we use a basic vanilla buttercream with some of the marshmallow meringue folded in!

Ingredients

Here are some tips, tricks and substitute suggestions for some of the key ingredients in this s’mores cake. If you have any other substitution questions, feel free to drop them in the comments!

• Buttermilk: Buttermilk helps tenderize the cake crumb and provides acid to react with the baking soda. If you don’t have buttermilk on hand, I often use half yogurt, half milk as a substitute. Either Greek yogurt or regular plain or vanilla yogurt will work, and you can use any kind of milk for the other half (I typically use whole or soy milk).
• Hot coffee: It’s key to add hot coffee to the batter to help bloom the cocoa powder–this unlocks the flavor compounds in cocoa for a more intense chocolate flavor. If you don’t have coffee on hand, you can use hot water mixed with 2 tsp of espresso powder or instant coffee.
• Neutral oil: Although canola or vegetable oil are some of the most common neutral oils for baking, you can also use avocado, grapeseed, safflower, algae, refined coconut or even a light olive oil. The cocoa generally overpowers the taste of most neutral oils in the final product.
• Eggs: I always use large eggs when baking. In this recipe, we’re using the egg yolks in the cake and saving the egg whites to make the meringue topping–don’t throw them out! It’s best to bring the eggs to room temperature before baking.
• Dutch-process cocoa powder: I prefer Dutch-process cocoa powder in most chocolate cakes (except Texas sheet cake) for its deeper color and flavor. However, you can also use natural cocoa powder here if that’s all you have (with both baking powder and baking soda in the recipe, there’s no need to modify anything if using natural cocoa).
• Graham cracker crumbs: Graham cracker crumbs make the graham crumb a breeze! If you don’t have ready-made crumbs on hand, you’ll need about half a pack of regular graham crackers. You can crush them into crumbs in a food processor or in a plastic bag with a rolling pin.
• Cream of tartar: This acidic ingredient helps make whipped egg whites more consistent and stable, which is key since we’re topping the cake with a large amount of marshmallow meringue. Without, the meringue might be more prone to collapsing or weeping. If you don’t have cream of tartar on hand, you can add double the amount of lemon juice or vinegar (I.e. 1/2 tsp) to the egg whites instead.
• Unsalted butter: I always prefer baking with unsalted butter in order to control the amount of salt in a recipe.

How to make this s’mores cake

Although this cake has four separate components, they come together relatively quickly. To make assembly a breeze, I recommend baking the cake and graham crunch a day or two ahead of time. You can keep both, wrapped well, in the fridge until ready to assemble the cake.

Storage and make ahead tips

This cake is a bit labor-intensive, so as I mentioned above, I highly recommend making some components ahead of time. The cake layers are also quite delicate while warm–my biggest tip for making this cake is to make sure your cake layers are COLD before handling!

• Cake: You can bake the cake at least a week ahead of time, wrap it well and freeze it. Let it defrost in the fridge overnight or at least 3 hours before you plan to assemble the final cake. I typically bake the cake a day before and keep it in the fridge overnight until ready to assemble.
• Graham crunch: You can also bake this up to a week ahead and keep it in an airtight container in the fridge until ready to assemble.
• Marshmallow meringue and buttercream: I recommend making these the day you plan to assemble the cake as the meringue tends to deflate a bit in the fridge.

Increase the meringue for frosting lovers: Note that the recipe as written will yield just enough meringue to incorporate into the buttercream and cover the cake with a bit extra for decorative swooshes. I loved the cake with this amount, but if you want a higher ratio of frosting to cake, see the recipes notes to increase the meringue amount (scaled to 4 egg whites). With this larger amount of meringue, you can add 3/4 cup to the marshmallow buttercream and swirl the meringue more generously on top of the cake!

Bake in a metal pan if possible: I prefer baking this cake in a metal 9×13 pan. Glass pans tend to heat up more quickly and retain more heat once they’re out of the oven–this can cause the edges of the cake to climb up the sides.

To make this cake vegan: I used all the components from The Banana Diaries’ vegan s’mores cake and assembled it in the same rectangular fashion and it worked so well! I was shocked by how well the aquafaba marshmallow meringue survived an entire picnic in the park. Highly recommend giving this a try if you need an eggless or vegan recipe!

Leftover cake can be stored in an airtight container in the fridge for at least a week. Individual slices can be frozen for at least a few weeks.