Ingredients
Scale
- 3 cups all-purpose flour
- 1 ½ teaspoons baking powder
- ¾ teaspoon baking soda
- 1 teaspoon salt
- 1 cup unsalted butter, softened
- 2 cups granulated sugar
- 4 large eggs, room temperature
- 1 tablespoon vanilla extract
- 1 ½ cups buttermilk, room temperature
- 1 cup unsalted butter, softened
- 3 ½ cups powdered sugar
- ½ cup unsweetened cocoa powder (Dutch-processed preferred)
- 3–4 tablespoons heavy cream
- 2 teaspoons vanilla extract
- ¼ teaspoon salt
Instructions
- Preparation: Preheat your oven to 350°F (175°C). Grease a 13×9-inch baking pan thoroughly with butter or non-stick cooking spray. For extra security, you can line the bottom with parchment paper, leaving an overhang on the sides to lift the cake out easily later. Sift your flour, baking powder, baking soda, and salt into a medium bowl and set it aside.
- Creaming the Butter and Sugar: In a large mixing bowl or the bowl of a stand mixer, beat the softened butter and granulated sugar together on medium-high speed. Continue mixing for about 3 to 5 minutes until the mixture looks pale and fluffy. Add the eggs one at a time, beating well after each addition, then stir in the vanilla extract.
- Mixing the Batter: Reduce the mixer speed to low. Add one-third of the dry ingredient mixture to the butter mixture, followed by half of the buttermilk. Repeat the process, ending with the final third of the dry ingredients. Mix only until the flour streaks disappear. Scrape down the sides of the bowl to ensure everything is incorporated.
- Baking the Cake: Pour the batter into the prepared baking pan and smooth the top with a spatula. Bake for 28 to 32 minutes. You will know it is done when a toothpick inserted into the center comes out clean or with just a few moist crumbs. Remove the pan from the oven and place it on a wire rack. Let the cake cool completely in the pan before you attempt to frost it.
- Making the Chocolate Buttercream: While the cake cools, prepare the frosting. Beat the softened butter until smooth and creamy. Sift in the powdered sugar and cocoa powder to avoid lumps. Add the heavy cream, vanilla, and salt. Start the mixer on low speed to avoid a sugar cloud, then increase to medium-high. Whip the frosting for 2 to 3 minutes until it is light, airy, and spreadable. Adjust the consistency with an extra splash of cream if needed.
- Frosting and Serving: Once the cake is entirely cool to the touch, dollop the chocolate buttercream over the top. Use an offset spatula to spread the frosting into an even layer, creating decorative swirls if desired. Cut the cake into 24 squares and serve directly from the pan.
- Cook Time: 50 minutes