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Mom's Chocolate Mint Brownie Cake Recipe - Flour Covered Apron

Mom's Chocolate Mint Brownie Cake

My mom's classic mint brownies were a favorite in our family growing up. This three-layer mint brownie cake, filled with chocolate ganache and a mint-flavored buttercream, uses the same recipe, just baked in six-inch round pans! 

Course Dessert
Cook Time 40 minutes
Servings 1 six-inch layer cake

Ingredients

Brownie Cake Layers

  • 4 ounces good quality semisweet chocolate, chopped
  • 1 1/3 cup unsalted butter (2 sticks + 5 1/3 tablespoons)
  • 5 large eggs, beaten
  • 2 2/3 cups sugar
  • 1/2 teaspoon salt
  • 1 1/2 teaspoons pure vanilla extract
  • 1 1/3 cups all-purpose flour

Mint Buttercream

  • 3/4 cups unsalted butter, softened
  • 4 cups powdered sugar
  • 1/4 teaspoons peppermint oil (or 1 1/2 teaspoons peppermint extract)*
  • pinch of salt
  • 3 tablespoons heavy whipping cream
  • 2-3 drops gel food coloring, green

Chocolate Ganache

  • 4 oz good quality semisweet chocolate, chopped
  • 4 tablespoons unsalted butter

Instructions

Brownie Cake Layers

  1. Preheat oven to 350 degrees Fahrenheit. Prepare 3 six-inch round cake pans by lining both the bottom and sides** with parchment paper and very generously buttering and flouring the pans.

  2. In a small saucepan, melt the chocolate and butter together over low heat, stirring frequently. Set aside to let cool slightly.

  3. In a large bowl, beat together the eggs and sugar until completely incorporated. Pour in the melted chocolate mixture and whisk to combine. Add salt, vanilla, and flour, then mix well.

  4. Divide evenly between the three cake pans, then bake at 350 degrees for 38-42 minutes. Top will be crackly and a toothpick inserted into the center should have a significant amount of moist crumbs attached (if toothpick comes out wet with batter, it's not done yet, but it shouldn't be totally clean, that means it's overbaked). Remove from oven and let cool for 5-10 minutes on a wire rack.

  5. Run a sharp knife around the edge of the pan to loosen the brownies, then turn out each layer onto a wire rack to cool completely.

Mint Buttercream

  1. Cream the butter until light and fluffy, then gradually add powdered sugar. Once incorporated, add peppermint oil and salt, then add cream one tablespoon at a time, mixing on low to incorporate.

  2. Add food coloring, then beat until incorporated and buttercream is smooth.

Chocolate Ganache

  1. In a small saucepan, melt the chocolate and butter together over low heat, stirring frequently. Once completely melted, remove from heat immediately. Pour into a glass jar or heatproof bowl, and let cool until it reaches a spreadable texture.

Assembling the Cake

  1. Secure the first brownie layer to a six-inch cardboard cake circle, or directly to a cake stand, using a small amount of buttercream. If desired, set aside some of the buttercream for piping on top, then spread about one third of the remaining buttercream on top of the first layer. Using an offset spatula, spread the frosting slightly beyond the edge on all sides. Top with about a third of the ganache and spread evenly on top of the buttercream with an offset spatula.

  2. Repeat with second layer, then top with third brownie layer, bottom side up. Top with the final third of the mint buttercream and ganache. Smooth the sides of the cake with an offset spatula or bench scraper. If desired, pipe any set-aside buttercream on top of the cake.

Recipe Notes

Cake is best served the day of, or the day after, but it will keep for a few days in the refrigerator. I recommend sealing the sides of the cake with saran wrap to store.

*Peppermint oil is much stronger than peppermint extract - don't confuse the two! But feel free to add a little more or less flavoring to taste

**Brownie cake can be difficult to remove from the pan. I highly recommend lining both the bottom and sides with parchment paper. Here's my method: butter the entire pan, then stick a circle of parchment paper to the bottom. Next, cut out a strip of parchment paper as wide as your cake pan is tall (2-3 inches), make it into a ring, then line the inner side of the cake pan as well. Finally, butter and flour the entire pan, on top of the parchment paper.