Ingredients
Scale
Chocolate Cake
- 2½ cups (300 g) all-purpose flour
- ¾ cup (about 64 g) natural unsweetened cocoa powder
- 2 cups (400 g) granulated sugar
- 2 teaspoons baking powder
- 1½ teaspoons baking soda
- ½ teaspoon fine salt
- 3 large eggs, room temperature
- 1 cup (240 ml) whole milk, room temperature
- ½ cup (120 ml) neutral vegetable oil
- 2 teaspoons vanilla extract
- 1 cup (240 ml) hot brewed coffee or hot water
Peanut Butter Buttercream
- 1½ cups (340 g) unsalted butter, softened
- 1½ cups (about 380 g) creamy conventional peanut butter
- 4½ cups (about 540 g) powdered sugar
- ⅓ to ½ cup (80–120 ml) heavy cream
- 2 teaspoons vanilla extract
- ¼ teaspoon fine salt
Chocolate Ganache
- 8 oz (225 g) semisweet chocolate, finely chopped
- ¾ cup (180 ml) heavy cream
Decoration
- 10–12 standard chocolate peanut butter cups, some whole and some halved
- Reserved peanut butter buttercream for piping
Instructions
- Prepare the pans. Preheat the oven to 350°F (175°C). Grease two 9-inch square cake pans. Line the bottoms with parchment paper and lightly grease the parchment.
- Mix the dry ingredients. In a large bowl, whisk together flour, cocoa powder, sugar, baking powder, baking soda, and salt. Break up any cocoa lumps.
- Mix the wet ingredients. In a separate bowl, whisk eggs, whole milk, vegetable oil, and vanilla until combined.
- Make the batter. Add the wet ingredients to the dry mixture. Mix on low speed just until combined. Slowly pour in the hot coffee while mixing. The finished batter will be fairly thin. This is normal.
- Bake. Divide the batter evenly between the prepared pans. Bake for 30–35 minutes, checking at about 28–30 minutes. A toothpick inserted near the center should come out without wet batter; a few moist crumbs are fine.
- Cool completely. Leave the cakes in their pans for 10–15 minutes. Turn them carefully onto wire racks and remove the parchment. Let them cool completely before frosting.
- Create four layers. For the tall appearance shown in the finished cake, chill the cooled cakes for about 30 minutes. Level any domed tops. Use a long serrated knife to split each cake horizontally. You should now have four square chocolate layers.
- Make the peanut butter buttercream. Beat softened butter for 2–3 minutes until creamy. Beat in the peanut butter until smooth. Add powdered sugar gradually on low speed. Add ⅓ cup heavy cream, vanilla, and salt. Beat for another 2–3 minutes. Add more cream, 1 tablespoon at a time, only if needed.
- Fill the cake. Place the first cake layer on a cake board or serving plate. Spread an even ⅓- to ½-inch layer of peanut butter buttercream over it. Repeat with the remaining layers to create four chocolate cake layers separated by three peanut butter filling layers.
- Crumb coat and chill. Spread a thin layer of buttercream over the entire cake to trap crumbs. Refrigerate for 30 minutes, or until firm.
- Apply the final frosting. Cover the chilled cake with a thicker, smooth coat of peanut butter buttercream. Reserve enough frosting for the top swirls. Chill again for 20–30 minutes before adding ganache.
- Make the ganache. Put finely chopped semisweet chocolate in a heatproof bowl. Heat the cream until steaming but not vigorously boiling. Pour it over the chocolate. Leave untouched for 2 minutes, then stir slowly until completely smooth and glossy.
- Test the drip. Allow the ganache to cool until fluid but no longer hot. Place one test drip on the back of the cold cake. If it reaches the cake board quickly, wait longer. If it barely moves, warm the ganache very gently.
- Decorate. Once the consistency is right, add ganache around the upper edges, allowing drips of different lengths to form. Spread a thin layer over the top.
- Finish the cake. Pipe generous peanut butter buttercream swirls around the top. Decorate with whole and halved chocolate peanut butter cups.
- Set before slicing. Chill briefly to firm the decoration. For a softer texture, allow the cake to lose some of its refrigerator chill before serving. Cut with a sharp knife and wipe the blade between slices.
Notes
- Cocoa: Use natural unsweetened cocoa powder for the formula as written.
- Coffee: Hot coffee strengthens the perception of chocolate flavor. Hot water can be substituted 1:1.
- Peanut butter: A conventional creamy peanut butter is preferable for predictable frosting consistency. Natural peanut butter that separates can make the buttercream oily or soft.
- Room-temperature ingredients: Bring eggs and milk close to room temperature before mixing.
- Do not add extra flour: This is intentionally a relatively thin chocolate batter.
- Cooling matters: Never split or frost warm cake.
- Straight layers: Chill the cakes before splitting if they feel fragile.
- Crumb coat: Do not skip it. Dark crumbs are especially visible through pale peanut butter frosting.
- Ganache: Always test one drip on the back first.
- Peanut allergy: This recipe contains peanuts and is unsuitable for anyone with a peanut allergy.
- Storage: Keep the decorated cake covered and refrigerated when storing for an extended period. Let slices soften slightly before serving for the best buttercream texture.
- Prep Time: 45 minutes
- Inactive / Chilling Time (+ Time): 1 hour 30 minutes
- Cook Time: 30–35 minutes
- Category: Dessert
- Method: Baking
- Cuisine: American