This S’mores Sheet Cake has a moist chocolate sheet cake slathered with toasted marshmallow icing and topped with buttered graham cracker crumbles. It is the perfect summer dessert!

This post is sponsored by JOHNSON & JOHNSON CONSUMER, Inc., McNeil Nutritionals, LLC Subsidiary the makers of LACTAID®. All opinions are 100% my own. Thanks for continuing to support the brands that help make ‘Kitchen 335’ possible!

A s'mores sheet cake topped with toasted marshmallow frosting and graham cracker crumbles.

I teamed up with LACTAID® to bring y’all your new summer staple: S’mores Sheet Cake! The chocolate sheet cake uses LACTAID® Whole Milk in the batter. LACTAID® is 100% real milk, just without the lactose. This means you don’t have to compromise flavor or texture to make your stomach happy! You can find LACTAID® Whole Milk at most retailers, but you can use this store locator to find exactly which stores near you carry it!

A carton of LACTAID Whole Milk surrounded by pieces of chocolate sheet cake

Ingredients for S’mores Sheet Cake:

Ingredients for Chocolate Sheet Cake:

  • All-Purpose Flour. Measuring the flour correctly is very important. I suggest weighing your flour out (I use this scale). If you want to use a measuring cup, make sure you spoon the flour into the cup and level it off with a knife. Don’t use the cup to scoop directly from the flour.
  • Cocoa Powder. This will give our sheet cake its chocolatey flavor.
  • Espresso Powder or Instant Coffee. You won’t actually be able to taste the coffee in the cake, but it will enhance the chocolate flavor.
  • Salt. Salt is a must in baked goods. It will help to balance out the sweetness and improve the overall flavor.
  • Baking Soda. This is a leavening agent that will help the cake to rise as it bakes.
  • Baking Powder. This will also help the cake rise.
  • Granulated Sugar. This is going to sweeten the cake.
  • Vanilla Extract. Vanilla is a must in baked goods just like salt. Real vanilla adds a better flavor than imitation vanilla.
  • Vegetable Oil. This will help make the chocolate sheet cake extra moist
  • Eggs. It will be easier to incorporate the eggs into the batter if they are at room temperature.
  • LACTAID Whole Milk. LACTAID is 100% real milk, just without the lactose! So you won’t be compromising the taste or texture of your sheet cake like you might with a dairy-free milk.

Ingredients for Marshmallow Icing:

  • Egg Whites. See above note.
  • Granulated Sugar. See above note.
  • Cream of Tartar. This will stregthen the whipped eggs whites. It’s not totally necessary, but it will make the icing stronger in the end.
  • Salt. See above note.
  • Vanilla Extract. See above note.

Ingredients for Graham Cracker Crumble:

  • Graham Crackers. Roughly crush the graham crackers for best results.
  • Unsalted Butter. I always make sure to use unsalted butter when baking because there is no “standard” for the amount of salt they can add to butter. So if you add salt to a recipe and then use salted butter you could end up with a very salty end product.
  • Granulated Sugar. See above note.
  • Salt. See above note.
All of the ingredients needed for this recipe

How to make S’mores Sheet Cake:

Chocolate Sheet Cake

STEP 1: Preheat oven to 350 degrees (F). Spray a 9×13 pan with non-stick spray and line with parchment paper or foil for easy removal once cooled.

STEP 2: In a large bowl whisk the flour, cocoa powder, espresso powder, salt, baking soda, and baking powder until well combined and free of lumps. Set aside.

The dry ingredients combined in a bowl

STEP 3: In the bowl of a stand mixer fitted with a paddle attachment or in a large bowl with a hand mixer beat the sugar and vegetable oil until light and fluffy.

STEP 4: Add the eggs one at a time, mixing well. Scrape down the sides of the bowl between each addition. Add the vanilla and combine.

The wet ingredients combined in a bowl

STEP 6: Slowly add the LACTAID Whole Milk to the sugar mixture, alternating with the dry ingredients. There should be at least 2 additions of the milk and dry ingredients.

STEP 7: Mix until just combined. Scrape down the sides of the bowl to ensure it is fully combined. Be sure to get the bottom of the bowl. The batter will be thin, this is okay.

The fully combined cake batter

STEP 8: Pour the batter into the prepared pan. Bake the cake for 30-35 minutes or until a toothpick inserted in the center of the cake comes out with only a few moist crumbs.

STEP 9: Remove the chocolate sheet cake from the oven and allow the cake to cool before frosting.

Marshmallow Icing

STEP 1: In the bowl of a stand mixer (you can use a hand mixer and a large, heat-proof bowl for this, but it will take quite a bit longer. I recommend a stand mixer if you have one available to you) combine the egg whites, sugar, cream of tartar, and salt.

STEP 2: Place the bowl over a saucepan with a couple of inches of simmering water.

STEP 3: Whisk the mixture constantly as it heats up. Whisk for about 6 minutes. The mixture should be warm to the touch and the sugar should be dissolved. If you have a thermometer you can heat the mixture to 115°F.

STEP 4: Transfer the bowl to the stand mixer fitted with the whisk attachment. Beat on high speed until stiff, glossy peaks form. This will take about 10 minutes.

STEP 5: Add the vanilla at the very end of mixing and beat until combined.

The marshmallow icing in a bowl

Graham Cracker Crumble

STEP 1: In a small bowl mix the graham cracker crumbles, melted butter, salt, and sugar until well combined.

The graham cracker crumbles in a bowl

How to Assemble a S’mores Sheet Cake:

STEP 1: If desired, remove the chocolate sheet cake from the pan before icing.

STEP 2: Spread the marshmallow icing on top of the chocolate cake. I recommend using a kitchen torch to toast the icing, but you can also place it under the broiler in your oven, just be sure to watch it very closely.

STEP 3: Sprinkle the buttered graham cracker crumbles on top of the toasted marshmallow icing. Slice and enjoy!

A close up shot of a slice of s'mores sheet cake on a plate

How to Store S’mores Sheet Cake:

This cake should hold up fine overnight at room temperature if you wrap the pan tightly with saran wrap or foil. However, the icing will start to deflate and won’t last much past that. So if you want to prepare ahead of time you can make the cake, freeze or refrigerate it, and make the icing when you are ready to serve.

Looking down on an entire sheet cake

More Sheet Cake Recipes

Two slices of cake on a plate

More Cake Recipes From Kitchen 335

  • Devil’s Food Sheet Cake– a rich and moist chocolate sheet cake topped wtih a honet and peanut butter flavored buttercream.
  • Lemon Poppy Seed Cake– a fluffy lemon and poppy seed cake topped wtih a whipped cream cheese frosting.
  • Pumpkin Cake– a moist pumpkin cake topped with whipped cream cheese frosting and caramel sauce.
  • Maple Coffee Cake– a fluffy and moist coffee cake swirled with a cinnamon streusel and topped with a sweet maple glaze.
A close up shot of a slice of chocolate cake topped with toasted marshmallow icing

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5 from 1 vote

S’mores Sheet Cake

This S'mores Sheet Cake has a moist chocolate sheet cake slathered with toasted marshmallow icing and topped with buttered graham cracker crumbles.
Prep Time30 mins
Cook Time35 mins
Total Time1 hr 5 mins
Course: Dessert
Cuisine: American
Keyword: Chocolate, chocolate cake, chocolate chip marshmallow cookie dough, Graham Cracker, marshmallow icing, s’mores, s’mores sheet cake
Servings: 16 slices
Calories: 277kcal

Ingredients

For Chocolate Sheet Cake:

  • 1 3/4 cup (210 grams) all-purpose flour
  • 1/2 cup (45 grams) cocoa powder
  • 1 teaspoon espresso powder or instant coffee
  • 1 teaspoon salt
  • 1 teaspoon baking soda
  • 1 teaspoon baking powder
  • 1 3/4 cup (346 grams) granulated sugar
  • 1/2 cup vegetable oil
  • 2 large eggs
  • 1 teaspoon vanilla extract
  • 1 1/2 cups LACTAID Whole Milk

For Marshmallow Icing:

  • 3 large egg whites
  • 3/4 cup (150 grams) granulated sugar
  • 1/2 teaspoon cream of tartar
  • 1/4 teaspoon salt
  • 1 teaspoon vanilla extract

For Buttered Graham Cracker Crumble:

  • 1 1/2 sheets graham crackers roughly crushed
  • 1/2 tablespoon unsalted butter melted
  • 1/2 tablespoon granulated sugar
  • 1/4 teaspoon salt

Instructions

For Chocolate Sheet Cake:

  • Preheat oven to 350 degrees (F). Spray a 9×13 pan with non-stick spray and line with parchment paper or foil for easy removal once cooled.
  • In a large bowl whisk the flour, cocoa powder, espresso powder, salt baking soda, and baking powder until well combined and free of lumps. Set aside.
  • In the bowl of a stand mixer fitted with a paddle attachment or in a large bowl with a hand mixer beat the sugar and vegetable oil until light and fluffy.
  • Add the eggs one at a time, mixing well and scraping down the sides of the bowl between each addition. Add the vanilla and combine.
  • Slowly add the milk to the sugar mixture, alternating with the dry ingredients.
  • Mix until just combined. Scrape down the sides of the bowl to ensure it is fully combined. The batter will be thin.
  • Pour the batter into the prepared pan. Bake the cake for 30-35 minutes or until a toothpick inserted in the center of the cake comes out with only a few moist crumbs.
  • Remove the cake from the oven and allow the cake to cool before frosting.

For Marshmallow Icing:

  • In the bowl of a stand mixer combine the egg whites, sugar, cream of tartar, and salt.
  • Place the bowl over a saucepan with a couple of inches of simmering water. 
  • Whisk the mixture constantly as it heats up. Whisk for about 6 minutes. The mixture should be warm to the touch and the sugar should be dissolved. If you have a thermometer you can heat the mixture to 115°F. 
  • Transfer the bowl to the stand mixer fitted with the whisk attachment. Beat on high speed until stiff, glossy peaks form. This will take about 10 minutes.
  • Add the vanilla at the very end of mixing and beat until combined. 

For Graham Cracker Crumble:

  • In a small bowl mix the graham cracker crumbles, melted butter, salt, and sugar until well combined.

S'mores Sheet Cake Assembly:

  • If desired, remove the chocolate sheet cake from the pan before icing.
  • Spread the marshmallow icing on top of the chocolate cake. I recommend using a kitchen torch to toast the icing, but you can also place it under the broiler in your oven, just be sure to watch it very closely. 
  • Sprinkle the buttered graham cracker crumbles on top of the toasted marshmallow icing.

Nutrition

Serving: 1slice | Calories: 277kcal | Carbohydrates: 47g | Protein: 4.3g | Fat: 9.3g | Saturated Fat: 2.5g | Cholesterol: 27mg | Sodium: 272mg | Potassium: 152mg | Fiber: 1.3g | Sugar: 33.4g | Calcium: 51mg | Iron: 3mg
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