Go Back
–+ servings
Cosmic Brownie Cake for Fudgy Chocolate Birthday Bliss

Cosmic Brownie Cake for Fudgy Chocolate Birthday Bliss

A rich chocolate layer cake with fudgy layers and thick frosting, inspired by the classic Cosmic Brownie treat.
Print Recipe Pin Recipe
Prep Time 30 minutes
Cook Time 28 minutes
Chill Time 20 minutes
Total Time 1 hour
Course Dessert
Cuisine American
Servings 16 slices
Calories 300 kcal

Equipment

  • 8-inch round cake pans
  • Mixing Bowls
  • Whisk
  • electric mixer
  • Parchment paper
  • wire rack

Ingredients
  

For the Chocolate Cake

  • 2 cups all-purpose flour
  • 2 cups granulated sugar
  • ¾ cup unsweetened cocoa powder
  • 2 teaspoons baking powder
  • 1 ½ teaspoons baking soda
  • 1 teaspoon salt
  • 2 large eggs
  • 1 cup buttermilk
  • ½ cup vegetable oil
  • 2 teaspoons vanilla extract
  • 1 cup hot coffee or hot water

For the Fudgy Chocolate Frosting

  • 1 cup unsalted butter, softened
  • ⅔ cup unsweetened cocoa powder
  • 4 ½ cups powdered sugar
  • ½ cup heavy cream
  • 2 teaspoons vanilla extract
  • ¼ teaspoon salt
  • 6 ounces semi-sweet chocolate, melted and slightly cooled

For the Cosmic Topping

  • ⅓ cup rainbow candy-coated chocolate chips or rainbow confetti candy pieces
  • 2 tablespoons rainbow sprinkles optional

Instructions
 

Preparation

  • Preheat your oven to 350°F. Grease and line three 8-inch round cake pans with parchment paper.
  • Whisk the flour, sugar, cocoa powder, baking powder, baking soda, and salt in a large bowl until evenly blended.
  • Add the eggs, buttermilk, oil, and vanilla extract. Mix until smooth, then slowly stir in the hot coffee or hot water until the batter looks glossy.
  • Divide the batter evenly between the pans. Bake for 22 to 28 minutes, or until a toothpick comes out with a few moist crumbs. Cool in the pans for 10 minutes, then transfer to a wire rack.
  • Beat the butter until creamy. Add the cocoa powder, then gradually beat in the powdered sugar. Mix in the heavy cream, vanilla, salt, and melted chocolate until thick and silky.
  • Trim the tops if needed so the cake layers stack evenly.
  • Place one layer on a serving plate and spread frosting over the top. Repeat with the second layer, then add the final layer.
  • Spread a thin layer of frosting over the entire cake. Chill for 15 to 20 minutes.
  • Cover the top and sides with the remaining frosting. Smooth it out or leave soft swirls.
  • Scatter the rainbow candy pieces over the top and gently press some around the sides. Add sprinkles if using.
  • Let the cake rest for 15 to 20 minutes before slicing so the frosting sets slightly.

Notes

Use room-temperature eggs, buttermilk, and butter for smoother mixing. The batter will be fairly thin, and that is normal. Hot coffee deepens the chocolate flavor without making the cake taste like coffee. Do not overbake the layers if you want the crumb to stay soft and fudgy. Cool the cake completely before frosting to keep the layers from sliding. Chill the crumb coat before the final frosting layer for a cleaner finish. For a stronger cosmic brownie look, use candy-coated chocolate chips instead of standard sprinkles alone. Store covered at room temperature for 1 day or in the fridge for up to 5 days. Freeze unfrosted layers or individual slices for up to 2 months.

Nutrition

Serving: 1sliceCalories: 300kcalCarbohydrates: 42gProtein: 3gFat: 15gSaturated Fat: 9gPolyunsaturated Fat: 1gMonounsaturated Fat: 5gCholesterol: 40mgSodium: 180mgPotassium: 160mgFiber: 1gSugar: 25gVitamin A: 500IUCalcium: 30mgIron: 2mg
Keyword Birthday Cake, Celebration Dessert, chocolate cake, Cosmic Brownie, Fudgy Cake, Vegetarian
Tried this recipe?Let us know how it was!