Dessert: United States – Great Lakes United States (Michigan) – Detroit-Style Bumpy Cake

Serving Size: 12

Approximate Time

Prep 1 hr 10 min

Cook 35 min

Additional 1 hr 15 min

Total 3 hrs

Ingredients

- For the cake:
- 2 1/2 cups (312 g) all-purpose flour
- 2 cups (400 g) granulated sugar
- 1 cup (226 g) unsalted butter, softened
- 3 large eggs, approx. 5.3 oz (150 g) total
- 1 cup (240 ml) whole milk
- 1/2 cup (120 g) sour cream
- 2 tsp (8 g) baking powder
- 1/2 tsp (3 g) baking soda
- 1 tsp (6 g) fine salt
- 2 tsp (10 ml) vanilla extract
- For the American buttercream:
- 1 1/2 cups (340 g) unsalted butter, softened
- 6 cups (720 g) powdered sugar, sifted
- 2–4 tbsp (30–60 ml) heavy cream or whole milk, adjust for spreading consistency
- 2 tsp (10 ml) vanilla extract
- Pinch fine salt
- For the chocolate fudge "bumps":
- 12 oz (340 g) semisweet chocolate chips (or chopped semisweet chocolate)
- 14 oz (396 g) sweetened condensed milk (1 can)
- 2 tbsp (28 g) unsalted butter
- 1 tsp (5 ml) vanilla extract
- Pinch fine salt
- For the chocolate ganache:
- 12 oz (340 g) bittersweet chocolate, finely chopped (60–70% cacao)
- 1 1/4 cups (300 ml) heavy cream
- 2 tbsp (28 g) unsalted butter (optional, for shine)
- 1 tbsp (15 ml) light corn syrup (optional, for gloss)
- Finishing (optional):
- Sea salt flakes for sprinkling

Instructions

Short Description:
A tender, buttery sheet cake topped with a thick layer of American buttercream dotted with chocolate fudge "bumps" and finished with a glossy chocolate ganache that smooths over the bumps while preserving their textured appearance.

Regional Notes:
This Detroit-area version highlights the signature chocolate fudge "bumps" arranged atop rich buttercream before being covered in a smooth ganache, giving the cake its distinctive bumpy top and dense, fudgy contrast. It differs from a generic frosted sheet cake by adding cooked fudge dollops that are chilled and then enrobed in ganache for a uniquely tactile finish associated with Detroit local bakeries.

1. Preheat the oven to 350°F (175°C). Grease and line a 9x13-inch (23 x 33 cm) baking pan with parchment, leaving an overhang for easy removal.
2. In a medium bowl whisk together flour, baking powder, baking soda, and salt. Set aside.
3. In the bowl of a stand mixer or with a hand mixer, cream 1 cup (226 g) softened butter and 2 cups (400 g) granulated sugar on medium-high until light and fluffy, about 3–4 minutes. Add eggs one at a time, mixing well after each, then mix in 2 tsp (10 ml) vanilla.
4. Reduce speed to low and add the dry ingredients in three additions alternating with the milk and sour cream (begin and end with dry ingredients), mixing until just combined and scraping the bowl as needed.
5. Pour batter into the prepared pan and smooth the top. Bake until a toothpick inserted near the center comes out clean, 30–35 minutes. Cool in the pan on a wire rack 20 minutes, then lift out using the parchment and cool completely to room temperature on the rack.
6. While the cake cools, make the chocolate fudge "bumps": combine semisweet chocolate chips, sweetened condensed milk, and 2 tbsp (28 g) butter in a medium heavy saucepan over low heat. Stir constantly until the chocolate and butter are fully melted and mixture is glossy and smooth, about 3–5 minutes — do not boil. Remove from heat, stir in 1 tsp (5 ml) vanilla and a pinch of salt. Transfer to a shallow bowl, cover surface with plastic wrap, and chill until thickened and pipeable, about 30–45 minutes (mixture should hold shape when scooped).
7. Make the buttercream while the fudge cools: beat 1 1/2 cups (340 g) softened butter on medium speed until creamy, about 2 minutes. Gradually add powdered sugar, 1 cup (120 g) at a time, on low speed. Add 2 tbsp (30–60 ml) heavy cream as needed for consistency, scrape bowl, then add vanilla and a pinch of salt. Beat on high 1–2 minutes until light and fluffy. If too stiff for spreading, add an extra tbsp (15 ml) cream.
8. Spread a generous, even layer of buttercream over the cooled cake, leaving the surface smooth. Chill the frosted cake 10 minutes to slightly firm the buttercream.
9. Fit a piping bag with a round tip (about 1/2 inch / 12 mm) or use a pastry bag without a tip. Fill the bag with the chilled fudge mixture and pipe dome-shaped bumps across the buttercream, spacing them evenly (aim for 20–30 bumps depending on size). Alternatively, scoop small mounds with a spoon and place them on the frosting. Chill the cake until the fudge domes are firm, about 15–30 minutes.
10. Make the ganache: place chopped bittersweet chocolate in a heatproof bowl. Heat heavy cream in a small saucepan until it just begins to simmer; pour the hot cream over the chocolate and let sit 1 minute, then stir gently until smooth and glossy. Stir in 2 tbsp (28 g) butter and 1 tbsp (15 ml) corn syrup if using, until incorporated. Let ganache cool until warm and pourable but not hot (about 5–10 minutes).
11. Remove the chilled cake from the refrigerator. Place it on a wire rack set over a baking sheet. Slowly pour the ganache over the center of the cake and use an offset spatula to gently coax ganache toward the edges so it flows evenly and covers the bumps; allow ganache to drip down the sides for a smooth finish. If needed, spoon additional ganache onto any exposed buttercream between bumps.
12. Let ganache set at room temperature about 30–45 minutes, then refrigerate for 20–30 minutes to fully firm. Sprinkle a few sea salt flakes across the top if desired. Slice into squares to serve.
13. Store leftover cake covered in the refrigerator up to 4 days; bring slices to near room temperature before serving for best texture.