Bumpy Cake

Servings: 12-15 | Prep Time: 30 minutes | Cook Time: 30-35 minutes | Total Time: 3 hours (includes chilling)

What Is Bumpy Cake?

Bumpy Cake is a beloved Michigan dessert that combines three perfect layers: a moist devil’s food cake, thick stripes of creamy vanilla buttercream, and a glossy fudge icing poured over the top. The result is a stunning cake with distinctive “bumps” that reveal the buttercream underneath when sliced.

The original Bumpy Cake was created in 1913 at Sanders Chocolate & Ice Cream Shoppe in Detroit, Michigan by German-born confectioner Fred Sanders Schmidt. The story goes that Sanders was running low on buttercream while testing a new chocolate cake recipe. Instead of frosting the cake in a traditional layer, he playfully piped the remaining buttercream in rails across the top, then covered it with fudge icing. Customers loved the unique look and began calling it “the cake with the bumps”—and the name stuck.

What started as a happy accident became a Michigan icon, originally sold under the name “Sanders Devil’s Food Buttercream Cake” before being officially renamed Bumpy Cake. Today, it remains a beloved regional treat, celebrated for its rich chocolate flavor and nostalgic appeal.

Why You’ll Love This Recipe

This homemade version captures all the magic of the original. The chocolate cake is deeply rich and moist, thanks to the addition of hot coffee, which enhances the cocoa flavor without making it taste like coffee. The buttercream is smooth, sweet, and holds its shape beautifully. And the fudge icing? It’s glossy, pourable, and sets into a perfect chocolate shell that crackles when you slice through it.

While this cake requires some time and a few steps, it’s surprisingly straightforward. The payoff is a showstopper dessert that will impress anyone you serve it to.

Ingredients

For the Chocolate Cake:

1¾ cups all-purpose flour
1¾ cups granulated sugar
¾ cup unsweetened cocoa powder
1½ teaspoons baking powder
1½ teaspoons baking soda
1 teaspoon salt
2 large eggs
½ cup canola or vegetable oil
1 cup buttermilk (or whole milk)
1 teaspoon vanilla extract
1 cup hot brewed coffee (or hot water)

For the Vanilla Buttercream:

½ cup (1 stick) unsalted butter, softened
¼ cup vegetable shortening
4 cups powdered sugar, sifted
2 tablespoons milk or heavy cream
1 teaspoon vanilla extract
Pinch of salt

For the Fudge Icing:

½ cup buttermilk
1 cup granulated sugar
⅓ cup dark corn syrup
⅓ cup unsweetened cocoa powder
¼ teaspoon salt
1 cup (2 sticks) unsalted butter, cut into cubes and divided
2½ cups powdered sugar, sifted
2 teaspoons vanilla extract

Directions

Make the Cake:

1. Preheat and prepare. Preheat your oven to 350°F. Grease a 9×13-inch baking pan and line the bottom with parchment paper for easy removal.

2. Mix dry ingredients. In a large bowl, whisk together the flour, granulated sugar, cocoa powder, baking powder, baking soda, and salt until combined.

3. Add wet ingredients. Mix in the eggs and oil, then add the buttermilk and vanilla. Stir until combined. Gradually pour in the hot coffee and mix until the batter is smooth and free of any streaks. The batter will be thin.

4. Bake. Pour the batter into the prepared pan. Bake for 22 to 25 minutes, or until a toothpick inserted in the center comes out clean. Let the cake cool in the pan for 30 minutes, then transfer to the freezer to chill for at least 20 minutes.

Make the Buttercream:

5. Cream the butter and shortening.While the cake chills, make the buttercream. In a stand mixer with the whisk attachment, beat the butter and shortening on medium speed until pale and fluffy, about 2-3 minutes.

6. Add powdered sugar and liquids.With the mixer on low, gradually add the powdered sugar, then add the milk, vanilla, and salt. Increase speed and beat until smooth and creamy. The frosting should be thick enough to hold its shape when piped.

7. Pipe the bumps. Transfer the buttercream to a piping bag fitted with a large round tip (Wilton 1A works well). Pipe 4 to 7 straight lines across the length of the cake, spacing them about 1 inch apart. Each bump should be about ½ to 1 inch wide.

8. Freeze to set. Return the cake to the freezer for at least 30 minutes to firm up the buttercream bumps. This step is crucial—the cold buttercream will hold its shape when the warm fudge is poured over it.

Make the Fudge Icing:

9. Combine ingredients. In a medium saucepan over medium-low heat, combine the buttermilk, sugar, corn syrup, cocoa powder, salt, and half of the butter (1 stick). Heat and stir occasionally until the butter is melted and the mixture is combined.

10. Boil to temperature. Bring the mixture to a boil and cook until it reaches the soft-ball stage (235-240°F on a candy thermometer). This takes about 2-3 minutes of boiling. Do not let it go above 240°F.

11. Finish the fudge. Remove from heat and whisk in the remaining butter cubes, one at a time, until fully incorporated. Whisk in the powdered sugar and vanilla until smooth and glossy. Let the icing cool slightly until it’s still pourable but not too hot (about the consistency of pancake syrup).

Finish the Cake:

12. Pour the fudge. Remove the cake from the freezer. Pour the warm fudge icing in ribbons over the cake, making sure to completely cover the buttercream bumps and the entire surface. Work quickly, as the fudge will begin to set.

13. Chill to set. Return the cake to the freezer for 15-20 minutes to set the icing. Alternatively, refrigerate for at least 30 minutes.

14. Slice and serve. For clean slices, use a sharp knife and wipe it clean between cuts. Store leftovers in the refrigerator for up to 5 days.

Expert Tips

Use hot coffee in the cake. It intensifies the chocolate flavor without making the cake taste like coffee. Hot water works in a pinch.
Chill the cake before piping. A cold cake makes the buttercream easier to pipe and keeps the bumps intact.
Don’t rush the freezing. The buttercream bumps must be solid before you pour the fudge, or they’ll melt and lose their shape.
Temperature matters. The fudge icing should be warm enough to pour but not so hot that it melts the buttercream.
Pour in two layers. For complete coverage, pour half the fudge, let it set in the freezer for 10 minutes, then pour the rest.

Variations

Flavor twist: Try a vanilla or carrot cake version instead of chocolate.
Different buttercream: Use an ermine frosting for a more traditional Sanders-style texture.

Storage

Storage: Store in an airtight container in the refrigerator for up to 5 days.

Freezing: Freeze individual slices wrapped well for up to 3 months.

Final Thoughts

Bumpy Cake is more than just a dessert—it’s a piece of Michigan history. The rich chocolate cake, sweet buttercream bumps, and glossy fudge icing come together in a dessert that’s as beautiful as it is delicious. Whether you’re serving it for a birthday, a holiday, or just because, this nostalgic cake is guaranteed to impress.