Chocolate Sheet Cake with Milk Chocolate Frosting
This chocolate sheet cake is the kind of dessert that disappears fast at gatherings. Baked in a single pan, it delivers a soft, tender crumb with an intense chocolate flavor, then gets finished with a silky milk chocolate frosting that sets beautifully while staying creamy and smooth. It is simple enough for a casual family dessert, yet rich and impressive enough for celebrations, potlucks, or holidays.
The batter comes together on the stovetop and in one bowl, making it easy and reliable. Using a combination of bittersweet chocolate and Dutch-processed cocoa creates a deep, balanced chocolate taste, while milk and oil keep the cake moist for days. The frosting is made gently over a double boiler, giving it a glossy, luxurious texture that spreads effortlessly over the cooled cake.
Ingredients
For the Cake
- 1 ½ cups granulated sugar
- 1 ¼ cups all-purpose flour
- ½ teaspoon baking soda
- ½ teaspoon salt
- 1 cup whole milk
- 8 ounces bittersweet chocolate, finely chopped
- ¾ cup Dutch-processed cocoa powder
- ⅔ cup vegetable oil
- 4 large eggs, at room temperature
- 1 teaspoon vanilla extract
For the Milk Chocolate Frosting
- 1 pound milk chocolate, chopped
- ⅔ cup heavy cream
- 16 tablespoons unsalted butter, softened and cut into pieces
Instructions
Make the Cake
- Preheat the oven to 325°F (165°C). Position a rack in the center of the oven. Lightly grease a 9 x 13-inch baking pan with vegetable oil spray and set aside.
- In a medium bowl, whisk together the sugar, flour, baking soda, and salt until evenly combined. Set aside.
- In a large saucepan, combine the milk, chopped bittersweet chocolate, and cocoa powder. Place the saucepan over low heat and cook, whisking frequently, until the chocolate is fully melted and the mixture is smooth and glossy.
- Remove the saucepan from the heat and allow the chocolate mixture to cool slightly, about 5 minutes. Whisk in the vegetable oil, eggs, and vanilla extract until the mixture is smooth and well blended.
- Add the dry ingredients to the chocolate mixture and whisk gently until just combined, making sure to scrape the sides and bottom of the pan so no dry pockets remain.
- Pour the batter evenly into the prepared baking pan and smooth the top.
- Bake for 30 to 35 minutes, rotating the pan halfway through baking for even cooking. The cake is done when the center feels set and a toothpick inserted in the middle comes out with a few moist crumbs.
- Remove the cake from the oven and place the pan on a wire rack. Allow the cake to cool completely in the pan, about 1 to 2 hours, before frosting.
Make the Frosting
- While the cake is cooling, prepare the frosting. Place the chopped milk chocolate and heavy cream in a large heatproof bowl.
- Set the bowl over a saucepan filled with about 1 inch of gently simmering water, making sure the bottom of the bowl does not touch the water.
- Heat the mixture, whisking occasionally, until the chocolate is completely melted and the frosting is smooth and glossy, about 10 to 15 minutes.
- Remove the bowl from the heat. Add the softened butter and let it stand for about 5 minutes, then whisk until fully melted and perfectly smooth.
- Refrigerate the frosting without stirring until it has cooled and thickened to a spreadable consistency, about 30 minutes to 1 hour.
- Once ready, give the frosting a final whisk until smooth.
Assemble the Cake
Spoon the frosting into the center of the cooled cake and gently spread it outward to the edges using an offset spatula or the back of a spoon. Spread evenly over the surface.
Let the frosting set slightly before slicing. Cut the cake into squares and serve directly from the pan.
Tips for Best Results
- Allow the cake to cool completely before frosting to prevent the frosting from melting.
- Use good-quality chocolate for both the cake and frosting for the best flavor.
- This cake keeps well at room temperature for up to two days, covered, and stays moist even longer when refrigerated.
This chocolate sheet cake is rich, tender, and deeply chocolatey, with a smooth milk chocolate frosting that makes every bite irresistible.