Old Fashioned Buttermilk Chocolate Sheet Cake with Chocolate Frosting

four square slices cut into chocolate sheet cake on parchment paper with flowers, sprinkles, plates, and a white cheesecloth around.

Old Fashioned Buttermilk Chocolate Sheet Cake with Chocolate Frosting

Thick, extra chocolate-y, and SO DELICIOUS! This Old Fashioned Buttermilk Chocolate Sheet Cake with Chocolate Frosting is the perfect cake to bake for birthday parties, holiday's, weekend celebrations, or just as a weeknight dessert.

Course: Desserts

Cuisine: American

Prep Time: 25

Cook Time: 40

Total Time: 1 5

Servings: slices

Calories: 310kcal

Ingredients

Cake

2½ cups all purpose flour
⅔ cup Dutch process cocoa powder sifted
1⅓ cups granulated sugar
1 teaspoon salt
1 Tablespoon baking powder
3 large eggs room temperature
2 cups buttermilk
¾ cup vegetable oil
1½ teaspoons vanilla extract

Frosting

6¾ Tablespoons salted butter room temperature
2¼ cups powdered sugar sifted
⅔ cup Dutch process cocoa powder sifted
⅜ cup whole milk
1⅙ teaspoons vanilla extract

Instructions

Cake

Heat oven to 350℉/177℃.
Spray an 8-inch x 12-inch pan with baking spray. Set aside.
In a large bowl, whisk together flour, cocoa, sugar, salt, and baking powder.
Add eggs, buttermilk, oil, and vanilla.
Whisk until smooth, about 1-2 minutes.
Pour into prepared pan.
Bake for 40 minutes, or until cake tests done.
Allow to cool in pan.
Turn out, if desired.

Frosting

Combine all ingredients in a large bowl.
Beat with an electric mixer until smooth.
Spread on cooled cake.

Notes

Substitutions:

Don't have buttermilk? No worries! You can make your own. Measure out 2 cups of whole milk and add 2 Tablespoons of lemon juice. Let it stand about 10 minutes.
This recipe can be made vegan by using a plant-based homemade buttermilk (follow the directions above but with oat milk or soy milk), your favorite vegan egg replacement (we love aquafaba!). For the frosting, use your favorite vegan butter and plant-based milk.

Expert Tips:

Be careful not to over-mix the cake batter! If it's mixed too much, the cake may become tough and not rise properly.
If you want a thinner cake, use a 9-inch x 13-inch pan. Remember to reduce cook time!
If you’re unsure the cake is baked after the time listed below, you can use a cake tester or tooth pick. If it comes out clean, the cake is baked through!
Let the cake cool COMPLETELY before frosting it.
Make sure the butter and milk are room temperature before mixing the frosting.
Room temperature is about 70℉/21℃.
Remember to sift the cocoa powder and powdered sugar!
If frosting is too thick, you can add a little more milk.

Nutrition