Sheet Pan Chocolate Birthday Cake
Skip the store-bought birthday cake and make this sheet pan chocolate birthday cake instead! My homemade version consists of two layers of rich chocolate sponge decorated with a silky chocolate Swiss meringue buttercream and topped with chocolate ganache. Its rectangular shape makes it easier to decorate, transport, and cut slices for a crowd!
Equipment
Ingredients
For the cake layers:
- 320 g (2 ⅔ cups) all-purpose flour
- 450 g (2 ½ cups) granulated sugar
- 63 g (¾ cup) Dutch process cocoa powder
- 21 g (¼ cup) black cocoa powder
- 2 teaspoon baking powder
- 1 teaspoon kosher salt
- 300 g (1 ⅓ cup) whole milk, room temp
- 200 g (1 cup) neutral oil
- 3 eggs, room temp
- 1 tablespoon vanilla extract
- 150 g (¾ cup) freshly brewed coffee,
For the chocolate Swiss meringue buttercream:
- 210 g (about 6) egg whites
- 450 g (2 ¼ cups) granulated sugar
- 510 g (2 ¼ blocks) salted butter, room temp, but on the cooler side
- 170 g (1 cup) semisweet chocolate, melted
For the chocolate ganache:
- 170 g (¾ cup) heavy cream
- 113 g (4 oz) semisweet chocolate
- 28 g (2 tablespoon) unsalted butter, room temp
Instructions
For the cake layers:
- Preheat the oven to 350 degrees F. Grease and line one 9x13 cake pan with parchment paper.
- Soak cake strips in ice cold water.
- In a medium bowl, whisk together the flour, sugar, cocoa powders, baking powder, and salt. Set aside.
- In a large bowl, whisk together the milk, oil, eggs, and vanilla.
- Add the dry ingredients to the wet and whisk until just combined.
- Lastly, whisk in the hot coffee until fully combined.
- Pour half of the cake batter into the prepared pan (or divide between two 9x13 pans) and wrap the soaked cake strips around the outside of the pan. Weigh the batter for even cake layers.
- Bake for about 20-25 minutes or until a toothpick inserted comes out clean the cake pulls away from the sides of the pan.
- Turn the cake out onto a wire rack to cool completely. Repeat with the remaining half of the cake batter.
- Wrap the cake layers with plastic wrap and set aside until ready to assemble.
For the chocolate Swiss meringue buttercream:
- Wipe the bowl of a stand mixer and whisk attachment down with white vinegar.
- Add the egg whites and sugar to the bowl and whisk until fully combined.
- Place over a small saucepan of simmering water, and whisk frequently until it reaches 160 degrees F or until the sugar is completely dissolved and the mixture no longer feels grainy.
- Move the bowl over to the stand mixer with the whisk attachment. Whisk on medium-high speed until medium peaks form.
- Add the vanilla and continue whisking until stiff peaks form.
- Turn the mixer down to low speed, and wait until the meringue cools down to at least 85 degrees F.
- Cut the butter into cubes and add to the meringue a few pieces at a time, allowing them to fully incorporate before adding more.
- Once all of the butter is added, it may look curdled, but keep beating for a few more minutes and it will come together.
- Once the buttercream has mostly come together, change the whisk attachment to the paddle and keep mixing on low speed until homogenous and smooth.
- Lastly, mix in the melted chocolate on low speed until fully combined.
For assembly:
- Place the first cake layer on a serving tray (I used an upside down baking sheet). Add eight 3 tablespoon scoops of buttercream and spread into an even layer. Place the second cake layer on top and repeat.
- Spread an even layer of buttercream on the sides (crumb coat), then chill in the fridge for at least 10 minutes.
- Remove the cake from the fridge and apply a thicker layer of buttercream to the sides.
- Pipe buttercream along the edges of the cake as desired, then place in the fridge or freezer while you make the ganache.
For the ganache:
- In a small saucepan, place the heavy cream over low-medium heat. Stir frequently with a rubber spatula, and bring to simmer, or about 190 degrees F.
- Remove the pan from heat and add the chocolate and butter, and gently stir with a rubber spatula until fully combined.
- Immediately pour the warm ganache onto the cake and spread into an even layer. Allow to set at room temperature or in the fridge before slicing.
Notes
- Bake half the batter or use two pans. If you have two 9x13 cake pans, you can divide the batter between them and bake. If not, simply pour half the batter into your pan (weigh it for best results), bake, and repeat with the remaining batter. Be sure to let the pan cool before baking the second layer!
- Black cocoa powder substitute: If you do not have black cocoa powder, you can use an equal amount of dutch process cocoa powder, making it a total of 84g or 1 cup.
- Use cake strips to create flat cake layers. Soak these wilton cake strips in ice water before starting the cake batter. Just before baking, wrap the cake strips around the pan. The cold temperature on the outside of the cake will prevent the edges from baking faster than the center, resulting in an evenly baked flat cake.
- Wait until meringue cools down before adding butter. It is SO important to wait until the meringue drops down to at least 85 degrees F or you will risk the butter melting and the whole thing turning into a big soupy mess.
Nutrition Facts
Serving: 1large slice | Calories: 1099kcal | Carbohydrates: 114g | Protein: 10g | Fat: 71g | Saturated Fat: 35g | Polyunsaturated Fat: 12g | Monounsaturated Fat: 18g | Trans Fat: 2g | Cholesterol: 158mg | Sodium: 601mg | Potassium: 383mg | Fiber: 5g | Sugar: 86g | Vitamin A: 1440IU | Vitamin C: 0.1mg | Calcium: 126mg | Iron: 4mg
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