Chocolate Sheet Cake

INGREDIENTS

For the Cake

• 3 cups all purpose flour (360g)
• 2⅔ cups granulated sugar (530g)
• ½ cup Dutch-process cocoa powder (50g)
• 2 teaspoons baking soda
• 1½ teaspoons baking powder
• ¾ teaspoon salt
• 1 cup whole or low-fat buttermilk room temperature (240ml)
• ½ cup sour cream room temperature (120g)
• 3 large eggs room temperature
• ¾ cup vegetable oil (180ml)
• 1 tablespoon vanilla extract
• 1½ cups hot coffee or boiling water (360ml)

For the Frosting

• 1½ cup unsalted butter room temperature (340g)
• ¼ cup Dutch-process cocoa powder (25g)
• ¾ teaspoon salt
• 1 pound powdered sugar (450g)
• 1 to 3 tablespoons whole milk or heavy cream
• ⅓ cup hot fudge sauce or ganache (100g)
• Optional toppings (sprinkles, chopped nuts, shaved chocolate)

DIRECTIONS

For the Cake

1. Preheat the oven to 350ºF. Lightly grease a 9×13 inch cake pan with baking spray and line it with a parchment paper sling, if you plan on removing it from the pan.
2. In a large bowl sift together the flour, sugar, cocoa powder, baking soda, baking powder and salt and whisk to combine.
3. In a medium bowl, whisk together the sour cream, buttermilk, eggs, vegetable oil, and vanilla until combined. Slowly whisk in the hot coffee. Slowly pour the wet ingredients into the dry and whisk until no streaks of flour remain. Pour the batter into the prepared pan.
4. Bake for about 45 to 50 minutes or until the center of the cake feels springy when gently pressed and the edges of the cake start to pull away from the pan. Allow the cake to cool completely in the pan.

For the Frosting

1. In a large bowl or the bowl of a stand mixer fitted with a paddle attachment, beat the butter on medium speed until smooth and creamy, about 2 minutes. Add in the cocoa powder and salt and mix on low speed until fully combined, stopping to scrape down the bowl as needed.
2. With the mixer on low, gradually add in the powdered sugar ½ cup (60g) at a time. Stop and scrape down the bowl occasionally.
3. Once all the powdered sugar has been incorporated, add in the fudge or ganache and mix on medium-low speed until well combined. Beat in enough milk or cream until the frosting is smooth, fluffy, and easily spreadable.

Assemble the Cake

1. Once the cake has fully cooled, you can remove the cake from the pan and discard the parchment paper if desired. Spread the buttercream on top of the cake. I like to make it swoopy using an offset spatula, but you can have fun with it! Decorate as desired with sprinkles, chopped toasted nuts, or shaved chocolate.