If you love the cozy flavors of peanut butter combined with rich, melty chocolate, you are going to adore this Fudge-Filled Peanut Butter Cake Bars Recipe. It’s a delightful fusion of moist yellow cake and luscious fudge swirled right in, creating the perfect bite every time. These bars strike an unbeatable balance between peanut butter’s creamy nuttiness and the indulgent smoothness of chocolate fudge, making them an irresistible treat for any occasion. Simple to whip up yet stunningly satisfying, this recipe is perfect for sharing with family or keeping all to yourself as a delicious pick-me-up.

Ingredients You’ll Need
Getting ready to make these bars is a breeze because the ingredients are straightforward but pack a punch in flavor and texture. Each item has its role in bringing richness, sweetness, or that irresistible peanut butter charm.
- Yellow cake mix (15.25 oz): The base that keeps the bars tender and gives a light, fluffy texture.
- Creamy peanut butter (1 cup): Adds deep nutty flavor and creamy moisture that defines these bars.
- Unsalted butter, softened (1/2 cup + 2 tablespoons): Provides richness and smoothness, especially in the fudge layer.
- Large eggs (2): Bind everything together while helping the cake rise perfectly.
- Vanilla extract (1 teaspoon): Enhances the overall sweetness and rounds out flavors beautifully.
- Sweetened condensed milk (1 can, 14 oz): Key to the fudgy filling, offering creamy sweetness with a silky texture.
- Semisweet chocolate chips (1 1/2 cups): Give the fudge layer its signature chocolaty richness.
- Salt (1/4 teaspoon): Balances the sweetness and lifts all the flavors.
How to Make Fudge-Filled Peanut Butter Cake Bars Recipe
Step 1: Prepare the Base Layer
Start by preheating your oven to 350°F and generously grease a 9×13-inch baking pan to prevent sticking. In a large bowl, beat together the yellow cake mix, creamy peanut butter, softened butter, eggs, and vanilla extract. Mix until you get a thick, uniform dough that feels rich and slightly sticky. Press about two-thirds of this mixture firmly into the bottom of the pan, creating an even layer. This crust will be the sturdy foundation for your luscious fudge filling, so smooth it out carefully.
Step 2: Make the Fudge Filling
In a small saucepan over low heat, stir together the sweetened condensed milk, semisweet chocolate chips, 2 tablespoons of butter, and salt. Keep stirring gently but continuously until the chocolate melts fully and the mixture becomes silky smooth. This homemade fudge filling is what transforms these bars from everyday to extraordinary, adding gooey decadence right in the middle.
Step 3: Assemble the Bars
Pour the warm fudge mixture over the peanut butter base layer, using a spatula to spread it evenly across the pan. Then take the remaining peanut butter dough and crumble it evenly over the fudge layer. These crumbles bake into a slightly golden, textured topping that beautifully complements the fudgy center and soft crust below.
Step 4: Bake and Cool
Bake your creation for 25 to 30 minutes, or until the top turns golden and the bars feel set to the touch. Once out of the oven, allow them to cool completely in the pan so the fudge can firm up just right. This step is crucial because it makes slicing the bars neat and ensures every bite is perfectly gooey without being messy.
How to Serve Fudge-Filled Peanut Butter Cake Bars Recipe

Garnishes
Adding a sprinkle of chopped roasted peanuts on top before baking will introduce a delightful crunch that contrasts beautifully with the soft bars. Alternatively, dusting a tiny bit of powdered sugar just before serving can add an elegant touch without overpowering the peanut butter flavor.
Side Dishes
These bars are delicious on their own but pair surprisingly well with a scoop of vanilla ice cream or a dollop of whipped cream. If you want a refreshing balance, serve them alongside fresh berries to cut through the richness.
Creative Ways to Present
For a fun twist, cut the bars into small bite-sized squares and arrange them on a dessert platter for parties. You can also drizzle melted peanut butter or extra chocolate over the top before slicing to elevate their appearance and flavor. Wrapping individual bars in parchment paper makes an excellent handmade gift for friends and family.
Make Ahead and Storage
Storing Leftovers
These peanut butter cake bars stay fresh when stored in an airtight container at room temperature for up to three days. For longer storage, refrigerating them helps maintain their texture, keeping the fudge filling firm but the cake tender.
Freezing
To freeze, wrap the bars tightly in plastic wrap and place them inside a freezer-safe container or bag. They’ll keep well for up to three months. When ready to enjoy, thaw them overnight in the refrigerator to preserve that wonderful fudgy quality.
Reheating
If you prefer warm bars, gently reheat single servings in the microwave for 15 to 20 seconds. This melts the fudge just enough to make each bite luxuriously smooth and gooey without drying out the cake portion.
FAQs
Can I use peanut butter powder instead of creamy peanut butter?
Peanut butter powder won’t provide the same moisture and richness as creamy peanut butter, so it’s best to stick to the classic creamy version for this recipe to achieve the perfect texture and flavor.
Is it possible to make this recipe gluten-free?
Yes! Just substitute the yellow cake mix with a gluten-free cake mix of equal quantity. Make sure to check that your other ingredients, like chocolate chips, are also gluten-free.
What if I want a sweeter fudge layer? Should I use milk chocolate chips?
Absolutely, using milk chocolate chips will make the fudge layer sweeter and creamier. It’s a delicious variation if you prefer a milder chocolate flavor to complement the peanut butter.
Can I add chopped peanuts for extra texture?
Definitely! Adding chopped peanuts either on top before baking or mixed into the peanut butter dough gives a nice crunch that contrasts well with the soft bars and gooey fudge.
How thick should I press the base layer in the pan?
Press the peanut butter dough about evenly to cover the bottom of the 9×13-inch pan to form a solid 2/3 of the dough base. It should be firm but not too thin, which helps support the fudge filling without being overwhelming.
Final Thoughts
The Fudge-Filled Peanut Butter Cake Bars Recipe is truly one of those comforting desserts that feels like a warm hug in every bite. Easy enough for a casual bake-day and special enough to impress anyone, it’s perfect for sharing or indulging solo. I can’t recommend enough giving this recipe a try—you’ll wonder how you ever lived without these delectably fudgy, peanut buttery bars in your life.
Print
Fudge-Filled Peanut Butter Cake Bars Recipe
- Prep Time: 15 minutes
- Cook Time: 30 minutes
- Total Time: 45 minutes
- Yield: 24 bars
- Category: Dessert
- Method: Baking
- Cuisine: American
- Diet: Vegetarian
Description
These Fudge-Filled Peanut Butter Cake Bars combine the rich flavors of peanut butter and chocolate fudge into a moist, easy-to-make dessert. Using a yellow cake mix as the base, the bars feature a creamy peanut butter dough layered with a luscious chocolate fudge filling, baked to golden perfection. Perfect for any occasion, these bars are indulgent yet simple to prepare.
Ingredients
Peanut Butter Cake Bars
- 1 box yellow cake mix (15.25 oz)
- 1 cup creamy peanut butter
- 1/2 cup unsalted butter, softened
- 2 large eggs
- 1 teaspoon vanilla extract
Fudge Filling
- 1 can sweetened condensed milk (14 oz)
- 1 1/2 cups semisweet chocolate chips
- 2 tablespoons unsalted butter
- 1/4 teaspoon salt
Instructions
- Preheat Oven and Prepare Pan: Preheat your oven to 350°F (175°C) and grease a 9×13-inch baking pan to prevent sticking and ensure easy removal of the bars.
- Make Peanut Butter Cake Batter: In a large bowl, beat together the yellow cake mix, creamy peanut butter, softened butter, eggs, and vanilla extract until the mixture is well combined and thick in consistency.
- Form Base Layer: Press about two-thirds of the peanut butter cake batter evenly into the bottom of the prepared baking pan to create a solid base layer.
- Prepare Fudge Filling: In a small saucepan over low heat, combine the sweetened condensed milk, semisweet chocolate chips, 2 tablespoons of unsalted butter, and salt. Stir constantly until the mixture is fully melted and smooth, forming a rich fudge sauce.
- Assemble Layers: Pour the warm fudge mixture evenly over the peanut butter base layer in the pan, spreading it out carefully.
- Top Layer: Crumble the remaining one-third peanut butter cake batter over the fudge layer to create a textured top.
- Bake the Bars: Place the pan in the preheated oven and bake for 25 to 30 minutes, or until the top layer turns golden and is set firmly.
- Cool and Slice: Allow the bars to cool completely in the pan to set properly before slicing them into approximately 24 bars.
Notes
- For a crunchier texture, sprinkle chopped peanuts on top before baking.
- You can substitute milk chocolate chips for semisweet chocolate chips if you prefer a sweeter fudge layer.
- Ensure the peanut butter and butter are softened for easier mixing and better texture.
- Letting the bars cool completely before slicing helps in cleaner cuts and better presentation.

