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Frosted square of chocolate cake with sliced almonds, the kind of piece this easy chocolate cake recipe makes in a 9x13 pan
Chef Emma

Easy One-Bowl Chocolate Cake

A moist chocolate sheet cake mixed in one bowl with a whisk, made with cocoa, buttermilk, oil and hot coffee, and topped with an easy chocolate frosting.
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Prep Time 15 minutes
Cook Time 35 minutes
Cooling and frosting 1 hour 40 minutes
Total Time 2 hours 30 minutes
Servings: 16 squares
Course: Dessert
Cuisine: American
Calories: 340
Ingredients Equipment Method Notes

Ingredients
  

Cake
  • 1 3/4 cups all-purpose flour 220 g, spooned and leveled
  • 1 1/2 cups granulated sugar 300 g
  • 3/4 cup unsweetened cocoa powder 65 g, natural preferred
  • 1 1/2 tsp baking soda
  • 1/2 tsp baking powder
  • 1 tsp fine salt
  • 2 large eggs room temperature
  • 1 cup buttermilk 240 ml, room temperature
  • 1/2 cup neutral oil 120 ml
  • 2 tsp vanilla extract
  • 3/4 cup hot coffee or hot water 180 ml
Chocolate frosting
  • 1/2 cup unsalted butter 1 stick / 113 g, softened
  • 2 1/2 cups powdered sugar 300 g
  • 1/2 cup unsweetened cocoa powder 42 g
  • 1/4 cup milk 60 ml, plus more if needed
  • 1 tsp vanilla extract plus a pinch of salt

Equipment

  • 9x13-inch baking pan
  • Large bowl and whisk
  • Hand mixer (optional, for frosting)

Method
 

  1. Heat the oven to 350°F (175°C). Grease a 9x13-inch pan (line the bottom with parchment if you plan to turn the cake out).
  2. In a large bowl, whisk the flour, sugar, cocoa, baking soda, baking powder and salt for 30 seconds, breaking up lumps.
  3. Add the eggs, buttermilk, oil and vanilla and whisk until smooth, about 1 minute.
  4. Slowly whisk in the hot coffee or water. The batter will be thin.
  5. Pour into the pan and bake 30 to 35 minutes, until the top springs back and a toothpick in the center shows a few moist crumbs (about 205 to 210°F / 96 to 99°C inside).
  6. Cool completely in the pan on a rack, about 1 1/2 hours.
  7. For the frosting, beat the butter until creamy, mix in the powdered sugar, cocoa and salt, then beat in the milk and vanilla until smooth. Spread over the cooled cake and cut into 16 squares.

Notes

Layer cake: two 9-inch rounds, 25 to 30 minutes (double the frosting). Cupcakes: 24, 18 to 20 minutes. Do not eat the raw batter. Calories are an estimate per square from USDA FoodData Central values. Store covered at room temperature up to 2 days or refrigerated up to 5 days.