This buttery soft s’mores cake features a light vanilla cake layer on a crunchy graham cracker crust, finished with pillowy marshmallows and a glossy milk chocolate ganache. Baked in an 8×8 pan, this single-layer cake takes about 20 minutes of active prep and delivers classic s’mores flavor with minimal fuss.
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From the buttery graham cracker base to the tender vanilla crumb, marshmallow topping and silky chocolate ganache, this cake is all about texture and comfort. It’s simple to make—similar in ease to s’mores cookie bars—and faster than campfire-style s’mores while still delivering that nostalgic flavor.
As a longtime baker and busy parent, I favor recipes that look special but are easy to execute. This one-layer s’mores cake fits the bill: no elaborate decorating skills required and reliably delicious.
The cake batter is intentionally not overly sweet because the marshmallows and milk chocolate bring extra sweetness and nostalgia to each bite.
🍰 Cake ingredient notes
I tested variations of this recipe and learned that folding marshmallows directly into the batter causes them to melt away and leave gaps in the crumb. To keep the marshmallow flavor and texture, this version spreads the marshmallows on top of the baked cake so they soften and meld with the surface instead of dissolving into the batter.
Please refer to the printable recipe card at the end of this post for exact ingredient quantities and full baking directions.
Marshmallows — Mini marshmallows are ideal; they melt slightly and create that soft, bouncy topping.
Chocolate — Milk chocolate gives the familiar s’mores taste in the ganache. If you prefer dark or white chocolate, adjust the chocolate–cream ratio to achieve the right consistency.
Buttermilk — Buttermilk tenderizes the crumb and keeps the cake moist. Use store-bought buttermilk at room temperature for best results.
Eggs — Two large eggs at room temperature yield a better rise and softer texture.
Heavy cream — Use heavy or heavy whipping cream (about 36% fat) for the ganache so it sets properly; creams with less than 30% fat may produce a runny ganache.
Pro tip — To quickly bring eggs to room temperature, place them in a bowl of warm tap water for 5–10 minutes.
🥣 How to make this s’mores-inspired cake
Preheat the oven to 350°F (175°C). Line an 8×8-inch baking pan with parchment paper and set aside.
Make the graham cracker crust by crushing whole crackers in a food processor or a zip-top bag with a rolling pin. Mix the crumbs with melted butter and press firmly into the bottom of the lined pan. Set aside.
Whisk melted butter and sugar in a bowl until combined. Add vanilla, kosher salt and baking powder, whisking to incorporate.
Whisk in the eggs, then fold in half the flour. Add the buttermilk, stir, then add the remaining flour and mix until just combined.
Pour the batter over the prepared graham crust. Tap the pan gently on the counter a couple of times to release air bubbles.
Bake for about 26–28 minutes, or until the edges are set and a toothpick inserted into the center comes out with a few moist crumbs.
As soon as the cake comes out of the oven, scatter mini marshmallows over the hot surface so they soften and adhere to the cake. Use caution—the pan will be hot. Let the cake cool completely before adding the ganache.
When the cake has cooled, make the milk chocolate ganache: place finely chopped milk chocolate in a heatproof bowl. Warm the heavy cream until it just begins to simmer, pour it over the chocolate, let it sit for a minute, then stir until smooth and glossy.
Pour the ganache over the marshmallow-topped cake and spread gently with an offset spatula if needed. Sprinkle an additional crushed graham cracker over the ganache for garnish, if you like.
Allow the ganache to set for about an hour. Remove the cake from the pan, slice into pieces and serve.
Enjoy warm memories in a slice—perfect for family dessert or a special treat when you want classic s’mores without the campfire.
🎥 Video tutorial
A short video shows the cake coming together from crust to ganache. The ganache pour isn’t featured in my clip, but the written steps above explain it clearly.
👩🏻🍳 Tips for success
Weigh ingredients when possible for consistent results. After smoothing the batter over the crust, tap the pan on the counter 2–3 times to release air bubbles. Avoid overbaking—the cake should still show a few moist crumbs on a toothpick. Add marshmallows immediately after baking so they soften but don’t fully melt. When making ganache, chop the chocolate finely so it melts easily when the warm cream is added.
If you make this Simple One Layer S’mores Cake, please share a photo and tag me @twosugarbugs on Instagram — I love seeing your creations! Happy baking!
If you make this recipe {or any recipe} from two sugar bugs, please come back and leave a review and a ⭐️⭐️⭐️⭐️⭐️ rating. I read every comment and truly appreciate your feedback!
📖 Recipe
Simple One Layer S’mores Cake
recipe created and tested by:
Tasia Harper
For best accuracy, use weight (metric) measurements when available.
Please note
If you scale the recipe to 2x or 3x, grams may not auto-adjust—please verify weights when multiplying ingredients.
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Ingredients
Graham Cracker Crust
- 1 sleeve graham crackers 9 full sheets (140g)
- ¼ cup unsalted butter melted (57g)
Marshmallow Cake
- ½ cup unsalted butter melted (113g)
- ¾ cup granulated sugar (150g)
- 1 tablespoon pure vanilla extract
- ½ teaspoon kosher salt
- 2 teaspoons baking powder
- 2 large eggs room temperature
- 1 ¾ cup all-purpose flour* (219g)
- ⅔ cup buttermilk** (160mL)
- 2 cups mini marshmallows (96g)
Milk Chocolate Ganache
- 8 ounces milk chocolate chopped small (227g)
- ½ cup heavy cream (120mL)
- 1 sheet graham crackers (15g) crushed, for garnish
Instructions
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Preheat oven to 350°F (175°C). Line an 8×8-inch pan with parchment and set aside.
For the Graham Cracker Crust
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Crush graham crackers (1 sleeve / 9 full crackers / 140g). Mix with melted butter (¼ cup / 57g) and press into the bottom of the lined 8×8 pan. Set aside.
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In a bowl, whisk melted butter (½ cup / 113g) with sugar (¾ cup / 150g). Add vanilla (1 tbsp), kosher salt (½ tsp) and baking powder (2 tsp).
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Whisk in eggs (2 large). Add half the flour (of 1 ¾ cups / 219g total), mix until some flour remains, add buttermilk (⅔ cup / 160mL), then fold in the remaining flour until just combined.
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Pour batter over the crust and tap the pan 2–3 times to release bubbles. Bake 26–28 minutes, until edges are set and a toothpick shows a few moist crumbs.
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Immediately top the hot cake with 2 cups mini marshmallows (96g). Use caution—the pan will be hot. Let the cake cool completely before adding ganache.
Milk Chocolate Ganache
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Place finely chopped milk chocolate (8 oz / 227g) in a heatproof bowl. Heat heavy cream (½ cup / 120mL) until it simmers at the edges. Pour over the chocolate and let sit 1 minute.
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Stir until smooth and shiny, then spread the ganache over the cooled marshmallows. Garnish with crushed graham cracker (1 sheet / 15g) if desired. Let ganache set about 1 hour, slice and serve.
Notes
**Buttermilk can be substituted with kefir or with milk plus 2 teaspoons lemon juice or vinegar added to ⅔ cup and allowed to sit until slightly thickened.
This cake can be baked in a 9-inch cake round with 2–3″ sides; baking time is similar. Store leftovers at room temperature in an airtight container for 3–4 days or refrigerate; cover sides with parchment or plastic to retain moisture. Freeze up to 3 months; thaw overnight in the refrigerator.
Nutrition
Nutrition information is an estimate and may vary based on brands and portion sizes.