For the chocolate cake:
- 2 cups (250 grams) all-purpose flour
- 3/4 cup (65 grams) unsweetened cocoa powder
- 1 and 1/2 teaspoons baking soda
- 1 and 1/2 teaspoons baking powder
- 1 teaspoon salt
- 1 cup (200 grams) granulated sugar
- 1 cup (200 grams) brown sugar
- 1/2 cup (120ml) canola or vegetable oil
- 1 cup (240 ml) buttermilk
- 2 large eggs
- 2 teaspoons pure vanilla extract
- 1 cup (240 ml) boiling water
- 1 teaspoon instant espresso powder (optional)
For the chocolate frosting:
- 2 cups (460 grams) unsalted butter, softened to room temperature
- 6 cups (720 grams) powdered sugar
- 1 cup (90 grams) unsweetened cocoa powder, sifted
- 6-7 tablespoons (90-105 ml) heavy whipping cream
- 2 teaspoons vanilla extract
- 1/4 teaspoon salt
To make the chocolate cake:
Preheat oven to 350°F. Spray three 8-inch cake pans with nonstick cooking spray and line the bottom of each pan with parchment paper. Set aside.
In a large mixing bowl, sift together the flour, cocoa powder, baking powder, baking soda, and salt. Whisk in the granulated sugar and brown sugar until well combined. Then, add the oil, buttermilk, eggs, and vanilla extract and mix until just combined.
Add the instant espresso powder to the cup of boiling water and mix until fully dissolved. Add to the mixing bowl and mix until everything is just combined. The batter will be thin.
Evenly distribute the batter between all three cake pans. Bake at 350°F for 28-30 minutes or until a toothpick inserted into the center of the cakes comes out clean and the tops spring back when lightly touched.
Remove from the oven and transfer to a wire rack to cool completely.
To make the chocolate frosting:
In the bowl of a stand mixer fitted with the paddle attachment, or in a large mixing bowl using an electric mixer, beat the butter on medium speed for 1-2 minutes or until smooth.
Add the powdered sugar one cup at a time, making sure to mix well after each addition. Scrape down the sides of the bowl, then add the cocoa powder and mix until fully combined.
Add the heavy whipping cream, vanilla extract, and salt and mix on medium speed until fully combined, making sure to scrape down the sides of the bowl as needed.
To assemble the cake:
Level the tops of each cake with a knife or cake leveler. Place one of the cakes on a cake stand, top with a layer of frosting, and smooth it out into one even layer. Repeat with the second layer of cake. Place the third layer of cake on top and use the remaining frosting to frost the top and sides of the cake.