Quick Recipe Version (TL;DR)
Quick Ingredients
- 2 1/4 cups (295 g) all-purpose flour
- 2 cups (400 g) granulated sugar
- 3/4 cup (75 g) unsweetened cocoa powder
- 2 tsp baking powder, 1 1/2 tsp baking soda, 1 tsp fine salt
- 1 cup (240 ml) buttermilk, 1 cup (240 ml) hot coffee or water
- 1/2 cup (120 ml) vegetable oil, 3 large eggs, 2 tsp vanilla
- 1 3/4 cups (400 g) unsalted butter (for fillings/frosting)
- 7 cups (840 g) powdered sugar (for fillings/frosting/drizzle)
- 1 1/4 cups (315 g) creamy peanut butter + 1/4 cup (65 g) for drizzle
- 3/4 cup (75 g) unsweetened cocoa powder (for buttercream)
- 6–10 tbsp heavy cream or milk (for fillings/frosting/drizzle)
- 3–4 cups chopped Reese’s peanut butter cups + extra whole/halved for topping
Do This
- 1. Heat oven to 350°F (175°C). Grease and line three 8-inch round cake pans; chop Reese’s cups and set aside.
- 2. Whisk dry cake ingredients; whisk wet ingredients separately; combine, then stir in hot coffee or water. Divide batter between pans.
- 3. Bake 25–30 minutes until a toothpick comes out clean. Cool 15 minutes in pans, then fully on racks.
- 4. Beat peanut butter filling ingredients until fluffy. Beat chocolate buttercream ingredients until smooth and spreadable.
- 5. Layer cake: chocolate cake, peanut butter filling, generous handful of chopped Reese’s. Repeat, then top with final cake layer.
- 6. Crumb-coat and fully frost with chocolate buttercream. Decorate with chopped and whole Reese’s on top, drizzle with warmed peanut butter mixture, chill briefly, then slice and serve.
Why You’ll Love This Recipe
- A true candy bar lover’s dream: rich chocolate cake, creamy peanut butter filling, and plenty of Reese’s in every bite.
- Moist, tender cake layers that stay soft for days, even under all that frosting.
- Over-the-top bakery-style look, but made with straightforward, home-kitchen-friendly steps.
- Perfect make-ahead celebration cake for birthdays, potlucks, or any chocolate-peanut-butter craving.
Grocery List
- Produce: None required.
- Dairy: Buttermilk, unsalted butter, heavy cream (or whole milk), eggs.
- Pantry: All-purpose flour, granulated sugar, powdered sugar, unsweetened cocoa powder, baking powder, baking soda, fine salt, vegetable oil, vanilla extract, brewed coffee (or water), creamy peanut butter (no-stir), Reese’s peanut butter cups.
Full Ingredients
Chocolate Cake Layers (Three 8-inch rounds)
- 2 1/4 cups (295 g) all-purpose flour, spooned and leveled
- 2 cups (400 g) granulated sugar
- 3/4 cup (75 g) unsweetened cocoa powder
- 2 tsp baking powder
- 1 1/2 tsp baking soda
- 1 tsp fine sea salt (or table salt)
- 1 cup (240 ml) buttermilk, at room temperature
- 1 cup (240 ml) hot brewed coffee or hot water
- 1/2 cup (120 ml) neutral oil (vegetable, canola, or light olive)
- 3 large eggs, at room temperature
- 2 tsp pure vanilla extract
Peanut Butter Filling
- 3/4 cup (170 g) unsalted butter, softened to room temperature
- 1 cup (260 g) creamy peanut butter (no-stir style, not natural)
- 2 1/2 cups (300 g) powdered sugar, sifted if lumpy
- 1/4 tsp fine salt (omit if peanut butter is very salty)
- 2–4 tbsp heavy cream or milk, plus more as needed to reach spreadable consistency
Chocolate Buttercream Frosting
- 1 1/2 cups (340 g) unsalted butter, softened to room temperature
- 4 cups (480 g) powdered sugar, sifted if needed
- 3/4 cup (75 g) unsweetened cocoa powder
- 1/2 tsp fine salt
- 2 tsp pure vanilla extract
- 4–6 tbsp heavy cream or milk, plus more as needed for silky texture
Candy Add-Ins & Decoration
- 3–4 cups chopped Reese’s peanut butter cups (about 24–30 mini cups or 12–16 regular cups), divided
- 8–12 whole or halved Reese’s peanut butter cups for the top
Peanut Butter Drizzle
- 1/4 cup (65 g) creamy peanut butter (no-stir)
- 1/2 cup (60 g) powdered sugar
- 2–4 tbsp milk (add gradually until pourable)
- Pinch of salt (optional, to taste)
Step-by-Step Instructions
Step 1: Prepare the pans, oven, and candy
Preheat your oven to 350°F (175°C) with a rack in the center. Grease three 8-inch round cake pans with nonstick spray or butter, then line the bottoms with parchment paper rounds. Lightly grease the parchment as well to ensure easy release.
Unwrap your Reese’s peanut butter cups. Roughly chop 3–4 cups worth (these will go between the layers and around the sides) and set aside in a bowl. Reserve 8–12 whole or halved cups for decorating the top. Keep the candies in a cool place so they do not melt while you bake.
Step 2: Make the chocolate cake batter
In a large mixing bowl, whisk together the flour, granulated sugar, cocoa powder, baking powder, baking soda, and salt until evenly combined and no cocoa streaks remain.
In a separate medium bowl or large measuring jug, whisk together the buttermilk, oil, eggs, and vanilla until smooth. Pour the wet mixture into the dry ingredients and whisk just until you have a thick, mostly smooth batter.
Slowly pour in the hot coffee (or hot water) while whisking gently. The batter will be thin; this is what makes the cake moist and tender. Stir until fully combined and no streaks remain, scraping down the bowl as needed.
Step 3: Bake and cool the cake layers
Divide the batter evenly among the three prepared pans (about 2 to 2 1/4 cups of batter per pan). Tap each pan gently on the counter a few times to remove large air bubbles.
Bake for 25–30 minutes, or until the cakes spring back lightly when touched and a toothpick inserted in the center comes out with just a few moist crumbs, not wet batter.
Cool the cakes in their pans on a wire rack for 10–15 minutes. Then run a thin knife around the edges, carefully turn each cake out onto the rack, peel off the parchment, and allow to cool completely, at least 45 minutes. For easier decorating, you can wrap the cooled layers in plastic and chill them for 30–60 minutes.
Step 4: Make the peanut butter filling
In a medium bowl, beat the softened butter with an electric mixer on medium speed until smooth and creamy, about 1–2 minutes. Add the peanut butter and beat again until fully combined, light, and fluffy.
Gradually add the powdered sugar and salt, mixing on low speed at first to avoid a sugar cloud, then increasing to medium-high until the mixture is thick and fluffy. Add 2 tablespoons of cream or milk and beat again. If the filling feels too stiff to spread easily, add more cream 1 tablespoon at a time until you reach a smooth, spreadable consistency that will hold its shape between layers.
Set aside at cool room temperature while you prepare the chocolate buttercream.
Step 5: Make the chocolate buttercream frosting
In a large bowl, beat the softened butter on medium-high speed until very smooth and pale, about 2–3 minutes. In a separate bowl, whisk together the powdered sugar, cocoa powder, and salt.
Add about half of the sugar-cocoa mixture to the butter and mix on low speed until incorporated. Add the remaining sugar mixture, along with the vanilla and 4 tablespoons of cream or milk. Beat on low until combined, then increase speed to medium-high and whip for 2–3 minutes, until the frosting is thick, smooth, and fluffy.
If the buttercream seems too thick, add more cream 1 teaspoon at a time; if it is too soft, beat in a bit more powdered sugar. You want a spreadable frosting that will hold soft peaks and cling nicely to the cake.
Step 6: Assemble the cake with filling and chopped Reese’s
Place one cooled cake layer on a serving plate or cake stand. If the top is very domed, use a long serrated knife to level it. Spread a thin smear of chocolate buttercream over the cake to help anchor the filling.
Top with half of the peanut butter filling, spreading it evenly to the edges. Sprinkle generously with about 1 to 1 1/2 cups of the chopped Reese’s peanut butter cups, pressing them gently into the filling.
Place the second cake layer on top, pressing lightly to secure. Repeat: thin smear of chocolate buttercream (optional but helpful), then the remaining peanut butter filling, then another 1 to 1 1/2 cups chopped Reese’s.
Finish with the third cake layer, bottom side up for the flattest top. Press down gently to even everything out.
Step 7: Frost the outside and decorate
With an offset spatula or butter knife, spread a thin layer of chocolate buttercream over the entire cake (top and sides) to create a crumb coat. This traps any loose crumbs. Refrigerate the cake for 15–20 minutes to firm up.
Once chilled, apply a thicker, final coat of chocolate buttercream over the top and sides, smoothing or swirling as you like. While the frosting is still soft, press remaining chopped Reese’s up the sides of the cake or around the bottom edge for a candy-studded border.
Arrange the reserved whole or halved Reese’s peanut butter cups on top of the cake in a ring or decorative pattern, leaving space in the center for drizzle.
Step 8: Make the peanut butter drizzle and finish
In a small microwave-safe bowl, combine the 1/4 cup peanut butter and powdered sugar. Add 2 tablespoons of milk and a pinch of salt if using. Microwave in 10–15 second bursts, stirring in between, until the mixture is smooth, glossy, and just warm. Add more milk 1 teaspoon at a time if needed until it is pourable but still thick enough to cling.
Let the drizzle cool for a minute or two so it is not piping hot, then spoon it over the top of the cake, letting it drip slightly over the edges and around the Reese’s decorations. If you like a more controlled look, transfer the drizzle to a small piping bag or a zip-top bag with a tiny corner snipped off.
Chill the finished cake for at least 20–30 minutes to set the frosting and drizzle. Slice with a sharp, long knife, wiping the blade between cuts for clean layers, and serve.
Pro Tips
- Use room temperature ingredients. Room temp eggs, buttermilk, and butter help the batter and buttercreams come together smoothly without curdling.
- Chill the cake layers before stacking. Cool or lightly chilled layers are sturdier and less likely to crumble while you stack and fill.
- Do not overmix the batter. Once you add the hot coffee or water, mix just until combined to keep the cake tender.
- Crumb-coat for a clean finish. That first thin coat of frosting locks in crumbs and gives you a much neater final layer.
- Slice the Reese’s while cold. Slightly chilled peanut butter cups chop more cleanly and do not smear as much chocolate and peanut butter.
Variations
- Sheet cake version: Bake the chocolate cake in a 9×13-inch pan (bake 30–35 minutes), then spread with a layer of peanut butter filling, a layer of chopped Reese’s, and finish with chocolate buttercream and drizzle.
- Cupcake version: Bake the batter in lined muffin tins (about 20–22 cupcakes, 18–22 minutes). Core the centers, fill with peanut butter filling and chopped Reese’s, then top with chocolate buttercream and a mini peanut butter cup.
- Extra-chocolate ganache drip: For an even more dramatic look, add a ring of chocolate ganache drip under or over the peanut butter drizzle (use equal weights hot cream and chopped dark chocolate).
Storage & Make-Ahead
The fully assembled cake keeps well, covered, at cool room temperature for up to 1 day. For longer storage, refrigerate it, well covered, for up to 4–5 days. Let chilled slices sit at room temperature for 20–30 minutes before serving so the cake softens and the peanut butter filling becomes creamy again.
You can also make components ahead. Bake the cake layers up to 2 days in advance; wrap each cooled layer tightly in plastic wrap and store at room temperature, or freeze for up to 2 months. Thaw frozen layers, still wrapped, at room temperature before assembling. The peanut butter filling and chocolate buttercream can be made 1–2 days ahead; store in airtight containers in the refrigerator and bring to room temperature, then re-whip briefly before using.
Nutrition (per serving)
Approximate values per slice, based on 12 servings: about 880 calories, 56 g fat, 95 g carbohydrates, 11 g protein, and 76 g sugar. Actual values will vary depending on the specific brands of ingredients and how much candy and frosting you use.
