Bumpy Cake

Why You’ll Love This Recipe

I love how this cake combines simple ingredients into something truly special. The soft chocolate base pairs perfectly with the sweet buttercream “bumps,” and the fudge icing brings everything together with deep chocolate flavor. It looks impressive when sliced, but I find it surprisingly easy to assemble. Whenever I want a crowd-pleasing dessert, this is what I bake.

Ingredients

(Here’s a tip: Check out the full list of ingredients and measurements in the recipe card below.)

Cake
1 box devils food chocolate cake
Eggs, oil, and water according to box directions

Buttercream
4 tablespoons butter
1 1/2 cups powdered sugar
1/2 teaspoon vanilla extract
1 tablespoon milk
Pinch of salt

Fudge Icing
1/2 cup buttermilk
2 tablespoons corn syrup
1/2 cup butter
2/3 cup unsweetened cocoa powder
3 1/2 cups powdered sugar
Pinch of salt
1/2 teaspoon vanilla extract

Directions

I begin by preheating my oven to 350°F and greasing a 9×13-inch baking dish.

For the cake, I prepare the devil’s food cake batter according to the box directions using the listed eggs, oil, and water. I pour the batter into the prepared baking dish and bake it for the time indicated on the package. Once baked, I let the cake cool completely to room temperature.

To make the buttercream, I beat the butter in a medium bowl until smooth. I add the salt, powdered sugar, milk, and vanilla extract, then mix until creamy and smooth. I transfer the buttercream into a piping bag or plastic bag and chill it for about 15 minutes. After chilling, I cut a ¾-inch opening and pipe straight lines across the cooled cake, spacing them about 1 inch apart. I place the cake in the freezer while I prepare the fudge icing.

For the fudge icing, I add the buttermilk, corn syrup, butter, cocoa powder, and salt to a medium saucepan. I heat the mixture until it comes to a gentle simmer, then lower the heat and continue simmering for 3 minutes, stirring often. I gradually mix in the powdered sugar, one cup at a time, until smooth. I remove it from the heat and stir in the vanilla extract. I let the icing cool for about 10 minutes so it thickens slightly.

I remove the cake from the freezer and carefully pour the fudge icing over the top, making sure it completely covers the buttercream lines. I place the cake in the refrigerator for about 30 minutes to allow the icing to set before slicing and serving.

Servings And Timing

This recipe serves 12.
Prep time: 20 minutes
Bake time: According to cake box (usually 28–35 minutes)
Cooling and setting time: About 1 hour
Total time: Approximately 1 hour 35 minutes

Variations

I sometimes make the cake from scratch instead of using a boxed mix when I have extra time. For a richer flavor, I use dark cocoa powder in the fudge icing. I have also added a touch of espresso powder to deepen the chocolate taste. If I want a slightly less sweet version, I reduce the powdered sugar in the icing just a bit.

Storage/Reheating

I store the cake covered in the refrigerator for up to 5 days. Because of the buttercream and fudge topping, I prefer keeping it chilled. Before serving, I let slices sit at room temperature for about 10 to 15 minutes so the texture softens slightly.

FAQs

Why Is It Called Bumpy Cake?

I pipe thick lines of buttercream across the cake before adding the fudge icing, which creates the signature “bumps” when sliced.

Can I Make This Cake Ahead Of Time?

I often make it a day in advance and keep it refrigerated. The flavors develop nicely overnight.

Do I Have To Freeze The Cake Before Adding The Icing?

I place the cake in the freezer briefly so the buttercream firms up, which helps keep the piped lines intact when I pour the warm icing over the top.

Can I Use Homemade Chocolate Cake Instead Of Box Mix?

I can absolutely use my favorite homemade chocolate cake recipe if I prefer a fully from-scratch version.

How Do I Know When The Icing Is Ready To Pour?

I let it cool slightly until it thickens but is still pourable. It should spread easily without being too runny.

Conclusion

This Bumpy Cake is a true classic that never goes out of style. I love the rich chocolate cake layered with sweet buttercream and topped with smooth fudge icing. It is simple, nostalgic, and always a hit when I share it. Whenever I want a dessert that feels both traditional and indulgent, this is the cake I make.