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5 from 2 votes

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


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


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.


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