Decadent Dark Chocolate Sheet Cake with Rich Cocoa Frosting

This elegant dark chocolate sheet cake is the ultimate crowd-pleaser for any gathering. With its intense cocoa flavor and less sweet profile, this grown-up dessert offers a sophisticated chocolate experience that’s perfect for potlucks, parties, and special occasions. The moist, dark crumb and rich frosting come together in a simple oven-baked creation that will have everyone asking for seconds.

Ingredients

For the Cake:

• 2 cups all-purpose flour
• 1¾ cups granulated sugar
• ¾ cup unsweetened cocoa powder (Dutch-process preferred)
• 2 teaspoons baking soda
• 1 teaspoon baking powder
• 1 teaspoon salt
• 2 large eggs, room temperature
• 1 cup buttermilk
• ½ cup vegetable oil
• 2 teaspoons vanilla extract
• 1 cup boiling water

For the Frosting:

• ½ cup unsalted butter
• ⅓ cup whole milk
• ¼ cup unsweetened cocoa powder
• 3 cups powdered sugar
• 1 teaspoon vanilla extract
• Pinch of salt

Step-by-Step Instructions

Preheat your oven to 350°F (175°C). Grease a 9×13 inch baking pan and set aside.

In a large mixing bowl, whisk together flour, sugar, cocoa powder, baking soda, baking powder, and salt until well combined.

Add eggs, buttermilk, vegetable oil, and vanilla extract to the dry ingredients. Mix on medium speed until just combined, about 2 minutes.

Carefully pour in the boiling water and mix on low speed until the batter is smooth. The batter will be thin – this is normal.

Pour the batter into the prepared pan and bake for 30-35 minutes, or until a toothpick inserted in the center comes out clean.

Allow the cake to cool completely in the pan on a wire rack before frosting.

For the frosting, melt butter in a saucepan over medium heat. Whisk in milk and cocoa powder until smooth. Remove from heat and gradually whisk in powdered sugar, vanilla, and salt until the frosting is smooth and spreadable.

Spread the frosting evenly over the cooled cake. Let set for 30 minutes before slicing and serving.

Expert Tips

For an even richer chocolate flavor, use high-quality dark cocoa powder. The boiling water helps bloom the cocoa, intensifying its flavor and creating that signature moist crumb texture. If you’re serving this at a party, consider adding some chocolate shavings or fresh berries for an elegant presentation.

This cake stores beautifully at room temperature for up to 3 days when covered. For longer storage, refrigerate for up to a week. If you love chocolate desserts, you might also enjoy our decadent chocolate sheet cake or our easy one-bowl chocolate cake for simpler variations.

Frequently Asked Questions

Can I make this cake ahead of time?
Yes! This cake actually tastes even better the next day as the flavors have more time to develop. Frost it just before serving for the best texture.

What makes this cake “less sweet” compared to others?
We use a higher ratio of cocoa to sugar, and the dark cocoa powder has a more intense, slightly bitter chocolate flavor that balances the sweetness perfectly.

Can I use this recipe for cupcakes?
Absolutely! This batter works well for cupcakes – just reduce the baking time to 18-22 minutes. For more chocolate inspiration, check out our brick street chocolate cake recipe for another crowd-pleasing option.

Decadent Dark Chocolate Sheet Cake with Rich Cocoa Frosting

This elegant dark chocolate sheet cake is the ultimate crowd-pleaser with its intense cocoa flavor and less sweet profile, perfect for potlucks and special occasions. The moist, dark crumb and rich frosting come together in a simple oven-baked creation that stores beautifully and tastes even better the next day.

Print Recipe Pin Recipe

Prep Time 15 minutes mins

Cook Time 35 minutes mins

Total Time 50 minutes mins

Servings: 12 servings

Calories: 420

Ingredients Method Notes

Ingredients

  

Ingredients

• 2 cups all-purpose flour
• 1¾ cups granulated sugar
• ¾ cup unsweetened cocoa powder (Dutch-process preferred)
• 2 teaspoons baking soda
• 1 teaspoon baking powder
• 1 teaspoon salt
• 2 large eggs, room temperature
• 1 cup buttermilk
• ½ cup vegetable oil
• 2 teaspoons vanilla extract
• 1 cup boiling water
• ½ cup unsalted butter
• ⅓ cup whole milk
• ¼ cup unsweetened cocoa powder
• 3 cups powdered sugar
• 1 teaspoon vanilla extract
• Pinch of salt

Method

 

Instructions

1. Preheat your oven to 350°F (175°C). Grease a 9×13 inch baking pan and set aside.
2. In a large mixing bowl, whisk together flour, sugar, cocoa powder, baking soda, baking powder, and salt until well combined.
3. Add eggs, buttermilk, vegetable oil, and vanilla extract to the dry ingredients. Mix on medium speed until just combined, about 2 minutes.
4. Carefully pour in the boiling water and mix on low speed until the batter is smooth. The batter will be thin – this is normal.
5. Pour the batter into the prepared pan and bake for 30-35 minutes, or until a toothpick inserted in the center comes out clean.
6. Allow the cake to cool completely in the pan on a wire rack before frosting.
7. For the frosting, melt butter in a saucepan over medium heat. Whisk in milk and cocoa powder until smooth.
8. Remove from heat and gradually whisk in powdered sugar, vanilla, and salt until the frosting is smooth and spreadable.
9. Spread the frosting evenly over the cooled cake. Let set for 30 minutes before slicing and serving.

Notes

For an even richer chocolate flavor, use high-quality dark cocoa powder. The boiling water helps bloom the cocoa, intensifying its flavor and creating that signature moist crumb texture. This cake tastes even better the next day as the flavors have more time to develop.