One Layer Chocolate Cake (Sheet Cake)

A cake server with a slice of chocolate sheet cake with chocolate frosting.

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One Layer Chocolate Cake (Sheet Cake)

Moist chocolate birthday cake with a fudgy chocolate sour cream frosting.

Prep Time20

Cook Time35

Total Time55

Course: Dessert

Cuisine: American

Diet: Vegetarian

Servings: slices

Calories: 471kcal

Author: Ella Gilbert

Equipment

1 9x13-inch cake pan

Ingredients

Chocolate Cake

¾ cup cocoa powder dutch processed
1 ¾ cups granulated sugar
¾ teaspoon vanilla extract
¾ teaspoon kosher salt
2 eggs room temperature
2 cups all purpose flour
2 teaspoon baking soda
1 teaspoon baking powder
1 cup buttermilk room temperature
½ cup vegetable oil
1 cups very hot water

Chocolate Sour Cream Frosting

½ cup unsalted butter room temperature
pinch kosher salt
1 cup confectioners' sugar
½ cup cocoa powder dutch processed
¼ cup sour cream room temperature
3 oz dark chocolate chopped

Metric - US Customary

Instructions

Make Cake

Preheat your oven to 350°F/175°C. Butter or grease a 9x13-inch cake pan and then line with parchment paper. I recommend making a 'sling', so you have parchment paper overhanging, to make it easier to get the cake out!
Combine the flour, cocoa powder, sugar, baking powder, baking soda, and salt in a large bowl with a whisk.
¾ cup cocoa powder, 1 ¾ cups granulated sugar, 2 cups all purpose flour, 2 teaspoon baking soda, 1 teaspoon baking powder, ¾ teaspoon kosher salt
In a large jug, whisk together the buttermilk, oil, eggs, and vanilla extract.
¾ teaspoon vanilla extract, 1 cup buttermilk, ½ cup vegetable oil, 2 eggs
Slowly pour in the ingredients from the large jug and mix until just combined.
Slowly add the hot water and mix. Your batter will be very thin and it makes a lot of cake batter!
1 cups very hot water
Pour the batter into the prepared pans. Bake for 35-40 minutes, until a toothpick comes out clean when inserted
Allow the cakes to cool for 10 minutes before removing from the pan. Let them cool completely on a cooling rack.

Make Frosting

Melt your chocolate in a microwave, stirring every 10 seconds so it doesn't burn.
3 oz dark chocolate
In your stand mixer with the paddle attachment, or in a bowl with a handheld mixer, beat the butter and confectioners’ sugar on low speed until well combined
½ cup unsalted butter, 1 cup confectioners' sugar
Turn the speed to high for 2-3 minutes until light and fluffy.
Add in your cocoa powder and beat on low, then increase the speed to medium for 1-2 minutes.
½ cup cocoa powder
Add your sour cream, melted chocolate and salt and mix once more.
¼ cup sour cream, 3 oz dark chocolate, pinch kosher salt
Frost your cooled cake and enjoy!

Video

Notes

My recipes have been developed and tested in metric grams. I highly recommend using a weighing scale and measuring out your ingredients the metric way. I have provided a conversion to US cups but please note that I haven’t tested the recipe with this method. Just click on ‘US Customary’ above the ingredients to see the cup measurements.

I make sure that all of my ingredients are at room temperature before I start the recipe, so pull out all of the ingredients before you start baking.

Cake Pan: I'm using a 9x13-inch cake pan from NordicWare with tall sides (like I would use for brownies or cinnamon rolls), and not a quarter sheet pan. This recipe would have slightly too much batter for a quarter sheet pan.

Salt: If you don’t have kosher salt, halve the amount of salt called for in the recipe. 1 teaspoon kosher salt = ½ teaspoon fine salt.

Buttermilk: If you don’t have buttermilk, replace it with an equal amount of sour cream or full fat yogurt. You can also make your buttermilk, for every cup of buttermilk add 1 tablespoon of lemon juice to 1 cup of milk and let sit for 5 minutes.

Sour Cream: I haven't tested this frosting with a sour cream substitute, but you could probably get away with using Greek yogurt or full-fat yogurt!

Vegetable Oil: Use an unflavoured oil like canola oil if you don’t have vegetable oil.

Storage: Keep tightly wrapped in the fridge for up to 5 days. Let it come to room temperature before eating.

Making Ahead: You can make the cake ahead of time. Bake and then once completely cooled, wrap in plastic wrap tightly. Store in the fridge for up to 2 days or in the freezer for up to 2 months. If frozen, allow to defrost and come to room temperature before frosting the cake.

Nutrition