Classic Chocolate Sheet Cake with Rich Cocoa Frosting

This classic chocolate sheet cake is rich, moist, and topped with a silky cocoa frosting that melts into every bite. It’s the kind of cake that brings back childhood memories—simple, comforting, and made with pantry staples. Baked in a 9×13 pan, it’s perfect for family gatherings, potlucks, or weeknight dessert cravings.

Who is this Recipe For?

This recipe is perfect for:

• Chocolate lovers who want a deep cocoa flavor in every bite.

• Busy home bakers looking for a foolproof cake that doesn’t require fancy decorating.

• Families who need a large, crowd-friendly dessert.

• Beginner bakers since this recipe is straightforward and forgiving.

Why It’s Great

• One-bowl style prep: Easy mixing, no complicated steps.

• Moist and tender: Thanks to buttermilk and butter, the texture is perfect.

• Classic flavor: Deep cocoa cake paired with fudgy frosting makes it irresistible.

• Feeds a crowd: Cut into 15 squares—ideal for parties, birthdays, and holidays.

Ingredients

For the Cake

• 2 ½ cups all-purpose flour (plus extra for dusting pan)

• 2 cups granulated sugar

• 1 teaspoon baking soda

• ¼ teaspoon salt

• 2 sticks unsalted butter, cubed (plus extra for greasing)

• ½ cup Dutch cocoa powder, sifted

• 1 ½ cups water

• ½ cup buttermilk

• 2 eggs, lightly beaten

• 1 ½ teaspoons vanilla extract

For the Frosting

• 1 stick unsalted butter

• ½ cup Dutch cocoa powder, sifted

• 6 tablespoons buttermilk

• 1 teaspoon vanilla extract

• ¼ teaspoon salt

• 3 ½ cups powdered sugar

• ½ cup chopped walnuts or pecans (optional)

Instructions

Make the Cake

1. Preheat oven to 350°F (175°C). Grease and flour a 9×13-inch cake pan.

2. In a large bowl, whisk together flour, sugar, baking soda, and salt.

3. In a small saucepan, combine butter, cocoa powder, and water. Heat on medium-low, whisking until smooth.

4. Pour the cocoa mixture into dry ingredients and stir gently.

5. Add buttermilk, eggs, and vanilla. Mix until smooth.

6. Pour batter into prepared pan and bake for 28–32 minutes, or until a toothpick comes out clean.

7. Let cake cool completely in the pan.

Make the Frosting

1. Melt butter in a saucepan over medium-low heat.

2. Whisk in cocoa powder and buttermilk until smooth and slightly thickened (about 1 minute).

3. Remove from heat, then stir in vanilla, salt, and powdered sugar until smooth.

4. Pour warm frosting over cooled cake, spreading evenly.

5. Sprinkle nuts on top if desired.

6. Allow frosting to set for 1 hour before slicing.

Kitchen Equipment Needed

• 9×13-inch cake pan

• Mixing bowls

• Whisk and spatula

• Saucepan

• Measuring cups and spoons

• Cooling rack

Storage

• Room Temperature: Keep covered at room temp for up to 3 days.

• Refrigerator: Store in an airtight container for up to 5 days. Bring to room temperature before serving.

• Freezer: Wrap individual slices tightly and freeze for up to 2 months. Defrost overnight in the fridge.

FAQ

Can I make this cake ahead of time?
Yes! Bake the cake the day before, store it covered, and frost it right before serving.

Can I use natural cocoa instead of Dutch cocoa?
Yes, but Dutch cocoa gives a richer, smoother chocolate flavor.

What can I use instead of buttermilk?
Mix ½ cup milk with 1 teaspoon vinegar or lemon juice, let sit for 5 minutes, then use as a substitute.

Do I have to add nuts?
No—nuts are optional. The cake is delicious with or without them.

Conclusion

This classic chocolate sheet cake is the ultimate easy dessert: simple ingredients, big chocolate flavor, and a luscious frosting that ties it all together. Whether you’re baking for a birthday, potluck, or just because, this cake will always impress. It’s a timeless recipe worth keeping in your collection.