Dark Chocolate Peanut Butter Cup Cake w/ Salted Honey Peanut Butter Filling

This chocolate peanut butter cup cake starts with your favorite rich chocolate boxed cake mix, then gets a few simple upgrades to make it taste completely homemade. Espresso powder deepens the chocolate flavor, while olive oil makes the cake extra rich and moist. It’s layered with a creamy peanut butter filling, covered in silky dark chocolate ganache, and finished with peanut butter cups for the ultimate chocolate-peanut butter dessert.

Decadent, surprisingly easy, and perfect for birthdays, celebrations, or whenever a serious chocolate craving hits. Let’s get cookin’!

INGREDIENTS

CHOCOLATE CAKE

1 box chocolate cake or devil’s food cake mix
Eggs, according to package directions
Whole milk or buttermilk, in place of the water called for on the box 1:1
Olive oil, in place of the vegetable oil called for on the box
1 tsp espresso powder
1-2 tsp vanilla extract
½ tsp kosher salt

SALTED HONEY PEANUT BUTTER FILLING

1 cup creamy peanut butter, preferably convectional rather than natural
4 tbsp unsalted butter, softened
¾ cup powdered sugar
2 tbsp honey
1-2 tsp vanilla extract or vanilla bean paste
½ tsp kosher salt
1-3 tbsp heavy cream

WHIPPED DARK CHOCOLATE GANACHE BUTTERCREAM

8 oz dark or bittersweet chocolate, finely chopped, ideally 60-70%
¾ cup heavy cream
½ cup (1 stick) unsalted butter, softened
1 cup powdered sugar
2 tbsp unsweetened cocoa powder
1-2 tsp vanilla extract or vanilla bean paste
½ tsp kosher salt
1 tsp espresso powder, optional
1-2 tbsp heavy cream, as needed

FOR FINISHING

Flakey sea salt
Chopped dark chocolate and/or chopped peanut butter cups, optional

Instructions

1. Prep the pans
   Preheat the oven according to the temperature listed on your cake mix. Grease two 8- or 9-inch round cake pans and line the bottoms with parchment paper.

2. Upgrade the boxed cake mix
   Prepare the chocolate cake mix according to the package instructions, but make a few swaps: replace the water 1:1 with whole milk or buttermilk and replace the vegetable or canola oil with the same amount of olive oil.

   Add the eggs called for on the box, along with the vanilla, espresso powder, and salt.

   Mix until just combined and smooth. Avoid overmixing.

3. Bake
   Divide the batter evenly between the prepared pans. Bake according to the package directions, beginning to check the cakes toward the lower end of the suggested baking time.

   The cakes are done when a toothpick inserted into the center comes out clean or with just a few moist crumbs.

   Let cool in the pans for about 10–15 minutes, then turn out onto a cooling rack and cool completely before assembling.

4. Make the salted honey peanut butter filling
   Beat the peanut butter and softened butter together for 1–2 minutes until smooth and creamy.

   Add the powdered sugar, honey, vanilla, and salt. Beat until thick and fully incorporated.

   Add the heavy cream 1 tablespoon at a time, beating between additions. You want the filling creamy enough to spread but still quite thick—it should hold its shape between the cake layers rather than ooze out.

   I’d start with 1 tablespoon and probably stop at 2. The thick texture is part of what makes this filling so good.

5. Make the dark chocolate ganache

   Place the finely chopped dark chocolate in a heatproof bowl.

   Heat ¾ cup heavy cream in a small saucepan until steaming and just beginning to simmer around the edges. Don't boil it.

   Pour the hot cream over the chocolate and let it sit untouched for 2–3 minutes. Slowly stir from the center outward until the chocolate is completely melted and the ganache is smooth and glossy.

   Allow the ganache to cool completely to room temperature before continuing. It should still be soft and spreadable, but not warm.

6. Make the ganache buttercream
   Beat the softened butter for 2–3 minutes until creamy and slightly fluffy.

   Add the powdered sugar, cocoa powder, vanilla, salt, and espresso powder. Beat until smooth.

   Pour in the cooled dark chocolate ganache and whip for another 2–3 minutes until the frosting becomes silky, fluffy, and deeply chocolatey.

   If it's too thick for frosting, add heavy cream 1 tablespoon at a time. If it feels too soft, let it sit for several minutes or refrigerate it briefly before frosting.

7. Assemble the cake
   If necessary, trim the tops of the cooled cakes so they're relatively level.

   Place your first cake layer on a cake stand or serving plate. I recommend piping a ring of the chocolate buttercream around the outer edge to create a dam for the peanut butter filling.

   Spoon the salted honey peanut butter filling into the center and spread it into an even, generous layer.

   Place the second cake layer on top.

   Cover the top and sides of the cake with the whipped dark chocolate ganache buttercream.

8. Finish and serve
   Top with a small sprinkle of flaky sea salt. You can leave it there for a simple, elevated look or finish with chopped dark chocolate or a few chopped peanut butter cups.

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