This peanut butter snack cake with chocolate ganache frosting is an easy 8-inch-square dessert that delivers a tender peanut butter crumb beneath a smooth, rich chocolate topping. It makes 9 to 12 servings, needs just 20 minutes of preparation, bakes in 28 to 35 minutes, and is ready in about 1 1/2 hours including cooling and frosting time.
Every bite balances nutty, buttery sweetness with deep semisweet or bittersweet chocolate. The cake is sturdy enough for lunchboxes and casual gatherings, yet the glossy ganache makes it special enough for a dinner-party dessert table.
Jump to RecipeWhy You’ll Love This Recipe
This cake has the comfort of a classic peanut butter cookie and the finish of a chocolate dessert from a bakery case. The brown sugar keeps the crumb moist, while buttermilk gives the batter a soft texture and gentle tang that prevents the sweetness from feeling heavy.
An 8-inch square pan makes this recipe wonderfully manageable. You get a generous small-batch cake without having to stack layers, pipe decorations, or prepare a complicated filling.
The chocolate ganache is equally practical. It requires only chopped chocolate and warm cream, with optional butter for a shinier finish and a pinch of salt to sharpen the chocolate flavor.
If this combination is a favorite in your kitchen, you may also enjoy these chocolate peanut butter cupcakes for a more individual serving option.
Ingredients You’ll Need
Begin with 1 cup (125 g) all-purpose flour, 1 teaspoon baking powder, 1/2 teaspoon baking soda, and 1/2 teaspoon fine salt. These dry ingredients provide the cake’s structure and balanced lift.
The rich base comes from 1/2 cup (113 g) softened unsalted butter, 1/2 cup (128 g) creamy peanut butter, and 3/4 cup (150 g) packed light brown sugar. Use regular creamy, no-stir peanut butter rather than natural peanut butter, which can separate and make the batter oily or loose.
You will also need 2 large eggs at room temperature, 1 teaspoon vanilla extract, and 1/2 cup (120 ml) buttermilk. Room-temperature eggs blend more smoothly into the butter mixture, and buttermilk helps create a tender crumb.
For the topping, prepare 4 ounces (113 g) finely chopped semisweet or bittersweet chocolate and 1/2 cup (120 ml) heavy cream. One tablespoon of unsalted butter is optional for shine, while a pinch of salt is optional for a slightly more pronounced chocolate flavor.
- Prepare an 8-inch square baking pan.
- Keep the butter softened, not melted.
- Bring the eggs to room temperature before mixing.
- Have parchment ready for easy release.
How to Make It Step-by-Step
Step 1: Heat the oven to 350°F (175°C). Grease an 8-inch square baking pan, then line the bottom with parchment so the finished cake can be lifted out neatly after cooling.
Step 2: Whisk the flour, baking powder, baking soda, and salt in a medium bowl. Breaking up any small lumps now helps the leaveners distribute evenly throughout the batter.
Step 3: In a large bowl, beat the softened butter, peanut butter, and packed brown sugar for about 2 to 3 minutes. Stop when the mixture looks light, creamy, and well blended rather than dense or streaky.
Step 4: Beat in the eggs one at a time, waiting until the first is incorporated before adding the second. Mix in the vanilla extract, scraping down the sides of the bowl if needed.
Step 5: Add the dry ingredients in two or three additions, alternating each addition with some of the buttermilk. Mix only until the batter is combined, since overmixing can make the cake less tender.
Step 6: Spread the batter evenly in the prepared pan. Use a spatula to reach the corners and smooth the top so the cake bakes at an even thickness.
Step 7: Bake for 28 to 35 minutes. The cake is ready when the center springs back lightly and a toothpick inserted in the middle comes out with a few moist crumbs rather than wet batter.
Step 8: Cool the cake completely in the pan before adding frosting. A warm cake will soften the ganache and may cause it to slide or soak into the surface.
Step 9: Place the finely chopped chocolate in a heatproof bowl. Heat the heavy cream until steaming but not boiling, pour it over the chocolate, and let it stand undisturbed for 2 minutes.
Step 10: Stir from the center outward until the chocolate melts into a smooth ganache. Stir in the optional butter and pinch of salt, then let the mixture cool until it is thick enough to spread.
Step 11: Spread the ganache over the completely cooled cake. For especially tidy portions, chill the frosted cake for 15 to 20 minutes and use a warm, dry knife to slice it.
Pro Tips for the Best Texture
Softened butter should yield when pressed but still hold its shape. If it is melted, the creaming step will not create the same light texture, and the finished cake may become denser.
Measure the flour carefully by spooning it into a dry measuring cup and leveling the top, or use the listed 125-gram weight. Too much flour can make this small cake dry and mask the creamy peanut flavor.
Do not judge doneness by time alone. Ovens vary, so begin checking near the 28-minute mark and look for a lightly springy center with a few moist crumbs on the toothpick.
Ganache consistency is easy to adjust. If it is too thin, let it stand at room temperature or chill it briefly; if it becomes too firm, warm it gently and stir until spreadable.
For another peanut butter treat with a quick, snackable format, try these easy peanut butter haystacks alongside your next dessert spread.
Serving and Storage
Serve the cake in 9 generous or 12 smaller squares. Its chocolate topping is rich enough that small pieces feel satisfying, especially with coffee, cold milk, or a scoop of vanilla ice cream.
For a simple presentation, leave the ganache smooth and add a few chopped peanuts immediately after frosting. You can also finish each piece with a small pinch of flaky salt, provided the overall dessert does not need to remain nut-free.
Keep the cooled, frosted cake covered at room temperature for short-term serving, or refrigerate it when you need longer storage. Bring chilled pieces toward room temperature before serving so the crumb softens and the ganache becomes creamy.
When storing the cake, protect the frosting from touching plastic wrap by using a cake carrier or tall covered container. Chill the entire cake for 15 to 20 minutes before slicing if you want especially clean edges.
For a different chocolate centerpiece, compare this recipe with our classic chocolate cake. A quick single-serving idea is also available in these hot chocolate brownie mug cake shots.
More Peanut Butter Dessert Ideas
This snack cake is a dependable starting point for a relaxed dessert menu. The peanut butter and chocolate pairing is familiar, but the tender square format makes it less formal than a layer cake and easier to portion for a crowd.
For a lighter cupcake-style variation, take a look at these light and creamy peanut butter cupcakes. They are a useful choice when you want individual portions instead of squares from one pan.
You can also serve this cake as part of a mixed dessert table with fresh berries, chocolate cookies, or small candies. Keep the decoration restrained so the smooth ganache and peanut butter crumb remain the focus.
Peanut Butter Snack Cake With Chocolate Ganache Frosting
Ingredients
Method
- Heat the oven to 350°F (175°C). Grease an 8-inch square baking pan and line the bottom with parchment.
- Whisk together the flour, baking powder, baking soda, and fine salt in a medium bowl.
- Beat the softened butter, peanut butter, and brown sugar for 2 to 3 minutes, until light and creamy.
- Beat in the eggs one at a time, then mix in the vanilla extract.
- Add the dry ingredients in two or three additions, alternating with the buttermilk. Mix only until combined.
- Spread the batter evenly in the prepared pan and bake for 28 to 35 minutes, until the center springs back lightly and a toothpick comes out with a few moist crumbs.
- Cool the cake completely in the pan before frosting.
- Place the finely chopped chocolate in a heatproof bowl. Heat the cream until steaming but not boiling, pour it over the chocolate, and let it stand for 2 minutes.
- Stir the ganache from the center outward until smooth, then stir in the optional butter and pinch of salt.
- Let the ganache cool until thick enough to spread, then frost the cooled cake.
Notes
Final Thoughts
Peanut butter snack cake with chocolate ganache frosting is the kind of dessert that feels both homemade and polished. The batter comes together with familiar pantry ingredients, the bake time stays under 35 minutes, and the ganache transforms the simple square into a rich, inviting treat.
Make it when you need a dependable dessert for 9 to 12 servings, or bake it simply because a tender peanut butter cake sounds irresistible. Let it cool completely, give the ganache time to reach the right spreading consistency, and finish with clean warm-knife slices for the best presentation.