Peanut Butter Chocolate Layer Cake

April 23, 2026

Some cakes are all about height; this one is about layers of flavor. You get plush chocolate cake that stays tender thanks to milk, oil, and a full cup of hot water stirred in at the end, plus a thick peanut butter buttercream that tastes like the inside of a peanut butter cup—salty-sweet and totally unapologetic.

If you love the chocolate + peanut butter combo (same energy as my chocolate peanut butter favorites), this is the celebration cake to bake. The finishing touch is a simple chocolate ganache drip and a pile of Reese’s: chopped pieces between layers, halves on top, and crumbs everywhere they’ll stick.

Why You’ll Love This Recipe

The cake layers bake up dark and soft, not dry, because the hot water blooms the cocoa and loosens the batter into a smooth, pourable texture.
Peanut butter buttercream that actually tastes like peanut butter, thanks to 1 1/4 cups of peanut butter plus a pinch of salt to keep it from going flat.
Built-in crunch and candy pockets from chopped Reese’s tucked into the frosting (this is not a “hint of candy” situation).
Ganache that sets with a clean slice, made from just chocolate chips and heavy cream—shiny, rich, and easy to nudge into drips.
Showstopper look without fussy techniques—swirls of frosting, a drip, and candy do most of the decorating work.
Make-ahead friendly components: bake the layers and make the frosting ahead, then assemble when you’re ready to serve.

The Story Behind This Recipe

I wanted a layer cake that tastes like a peanut butter cup but slices like a classic birthday cake—clean layers, generous frosting, and a chocolate finish. After testing the balance, the real “yes” moment was folding chopped Reese’s into the peanut butter frosting so every bite gets that little candy chew against the creamy buttercream.

What It Tastes Like

It’s sweet (this is a nine-cup powdered sugar kind of cake), but the cocoa’s deep and the peanut butter has a roasted, salty edge that keeps it in check. You’ll smell chocolate the second you cut into it, and the ganache adds a fudgy richness. Texture-wise: tender, moist cake; thick, creamy frosting; and little crunchy-chewy Reese’s bits that make the layers feel extra loaded.

Ingredients You’ll Need

This recipe leans on natural unsweetened cocoa powder for a bold chocolate base, and hot water to deepen that cocoa flavor and give you a silky, thin batter that bakes up surprisingly plush. For the frosting, use room-temperature butter so it whips smooth before the peanut butter goes in—cold butter can leave little lumps that never fully disappear. For thinning the buttercream, water or milk both work (milk makes it a touch richer).

1 3/4 cups (228g) all purpose flour
2 cups (414g) sugar
3/4 cup (85g) natural unsweetened cocoa powder
2 1/4 tsp baking soda
1/2 tsp baking powder
1 tsp salt
1 cup (240ml) milk
1/2 cup (120ml) vegetable oil
1 1/2 tsp vanilla extract
2 large eggs
1 cup (240ml) hot water
2 cups (448g) unsalted butter, room temperature
1 1/4 cups (350g) peanut butter
9 cups (1035g) powdered sugar
6-7 tbsp (90-105ml) water or milk
6 Reeses, chopped
Pinch of salt
6 oz (1 cup) semi-sweet chocolate chips
1/2 cup (120ml) heavy whipping cream
8 Reeses, cut in half
Crumbled Reeses

How to Make Peanut Butter Chocolate Layer Cake

Make the chocolate cake batter.
In a large bowl, whisk together the flour, sugar, cocoa powder, baking soda, baking powder, and salt until the cocoa looks evenly dispersed (no dark streaks). Add the milk, vegetable oil, vanilla, and eggs, and whisk until the batter is smooth and glossy.
Stir in the hot water (this is the magic step).
Pour in the hot water and whisk just until combined. The batter will look noticeably thinner—more like a loose brownie batter than a thick cake batter. That’s exactly what you want for soft layers.
Bake the cake layers, then cool completely.
Divide the batter evenly between your cake pans and bake until the tops look set and a toothpick comes out with moist crumbs (not wet batter). Let the layers cool in their pans briefly, then turn out to cool completely. Don’t rush this—warm cake will melt the frosting fast. If you’re into chocolate layer cakes, my three-layer chocolate mousse cake is another good “plan ahead and chill” kind of dessert.
Make the peanut butter frosting.
Beat the room-temperature butter until it looks lighter and creamy. Add the peanut butter and pinch of salt and beat again until fully smooth and uniform (no streaks). Mix in the powdered sugar gradually so it doesn’t puff everywhere.
Adjust the frosting texture.
Add 6–7 tablespoons of water or milk, a little at a time, beating between additions. You’re aiming for frosting that’s thick enough to hold layers but soft enough to spread without tearing the cake—smooth, fluffy, and slightly elastic.
Fold in chopped Reese’s.
Stir the chopped Reese’s in by hand so you don’t pulverize them. You want pieces throughout—little candy pockets, not crumbs.
Assemble the layers.
Place one cake layer on your serving plate. Spread a generous layer of peanut butter frosting over the top, pushing it all the way to the edge (the Reese’s pieces should be visibly dotted through). Add the second layer and repeat, then place the final cake layer on top.
Frost the outside.
Cover the top and sides with the remaining frosting. Don’t stress about perfection—this cake looks great with soft swirls and texture, and the ganache will add polish.
Make the ganache.
Place the semi-sweet chocolate chips in a bowl. Heat the heavy whipping cream until hot, then pour it over the chips. Let it sit briefly, then stir until the ganache is smooth and shiny. It should be fluid but not watery.
Drip, decorate, and let it set.
Spoon the ganache over the top and gently nudge it toward the edges to create drips. Top with Reese’s halves and crumbled Reese’s. Let the ganache set before slicing so you get clean layers instead of a chocolate slip-and-slide. If you’re a fan of gooey chocolate + peanut butter desserts, you’d probably also love my chocolate peanut butter lava cookies.

Tips for Best Results

Use truly room-temp butter. If it still feels cool and firm, your frosting won’t whip as smoothly, and you’ll fight little butter bits the whole time.
Add the hot water last and whisk gently. Overmixing after the flour is in can make the layers bake up a little tougher; stop once it’s smooth.
Cool the layers completely before frosting. Even slightly warm cake will soften the peanut butter buttercream and cause sliding.
Thin the frosting slowly. That 6–7 tablespoon range matters—go one tablespoon at a time until it spreads easily but still holds its shape.
Let the ganache cool a few minutes before dripping. If it’s too hot, it’ll run straight down and puddle at the bottom instead of forming neat drips.

Variations and Substitutions

Water vs. milk in the frosting: Milk makes the buttercream slightly richer; water keeps it clean and sweet—both work well.
More candy inside: If you like extra texture, save a small handful of Reese’s crumbs to sprinkle between layers as you frost (in addition to the chopped pieces mixed into the buttercream). For a quicker peanut butter-chocolate fix on busy days, I’ll often make peanut butter chocolate rice cakes instead.

How to Serve It

Slice with a long, sharp knife and wipe the blade between cuts—especially once you hit the ganache and candy. This cake is rich, so slightly smaller slices still feel generous. If you want the frosting at its creamiest, let the cake sit at room temperature briefly before serving.

How to Store It

Store the cake covered in the fridge to keep the buttercream and ganache firm. For the cleanest slices, chill first—then let slices sit out just a bit before eating so the peanut butter frosting softens. If you’re making it ahead, decorate with the Reese’s halves and crumbs closer to serving so they look their best and don’t soften too much in the fridge.

Final Thoughts

If you’re craving that classic peanut butter cup flavor in true layer-cake form—soft chocolate crumb, thick peanut butter frosting, and a glossy ganache finish—this one delivers. Take your time cooling the layers, be generous with the frosting, and let the candy do the decorating.

Conclusion

If you want to compare notes with other bakers’ takes on this flavor combo, you can check out Peanut Butter Chocolate Layer Cake from Life Love and Sugar, Chocolate Peanut Butter Cake from Sally’s Baking, and Peanut Butter Chocolate Cake from Sugar Spun Run—then come back and make this Reese’s-packed version your own.