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The Best Chocolate Mint Sheet Cake

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Decadent chocolate cake with cream cheese mint buttercream, ganache stripes, and chocolate shavings!
Servings 20 servings, depending on slice size

Equipment

  • stripe cake scraper
  • 869 Ateco piping tip
  • 9x13 sheet pan

Ingredients

  • 3/4 cup buttermilk room temperature
  • 2/3 cup sour cream room temperature
  • 3 whole eggs room temperature
  • 1 egg white
  • 1/3 cup vegetable oil
  • 1 Tablespoon vanilla
  • 1 teaspoon mint extract
  • 1/4 cup flour
  • 1/4 cup cocoa powder
  • 1/2 cup mini chocolate chips
  • 1 15.25oz Duncan Hines Box Cake Mix I used "Dark Chocolate Fudge", but anything similar from other brands is fine.

Cream Cheese Mint Buttercream

  • 2 sticks (or 1 cup) unsalted butter left out at room temperature for 10 minutes
  • 8oz brick cream cheese
  • pinch of salt
  • 1 Tablespoon vanilla
  • 1/2-1 teaspoon mint extract (1/2 if you want it less minty. 1 teaspoon if you want it to be full minty).
  • 1/4 cup heavy cream
  • 7-8 cups powdered sugar
  • 1-2 drops light green food gel coloring

Ganache

  • 1-2 cups Ghirardelli melting chocolate wafers
  • 1/4 cup heavy cream

Extra

  • 1 cup chocolate shavings

Instructions

For the Chocolate Cake

  • Preheat the oven to 325 and prep a sheet cake pan (9x13) with nonstick spray or shortening + flour. Set aside.
  • In a large bowl, whisk together all the cake ingredients except for the cake mix. Sift in the cake mix (batter will be super thick), and stir until it's all combined (don't overmix!). Spread the batter out onto the prepared sheet cake pan.
  • Bake the cake for 25-27 minutes, then let cool completely in the pan before adding on the frosting.

For the Buttercream

  • In the bowl of a large stand mixer, whip up the butter an cream cheese until they're both light and fluffy (no little white bits!), about 1 minutes on medium speed.
  • Add in the salt, vanilla, mint extract, and heavy cream and mix to combine. With the mixer on low speed, add in the powdered sugar about 1/2 cup at a time, then turn on the mixer to the highest speed for 2 minutes to help make the buttercream light and fluffy again. Add in the food coloring, and mix again. If it's too soupy, you need more powdered sugar OR you can place it in the fridge for 20 minutes to bring the butter and cream cheese back to a more cooled temperature.
    Use a wooden spoon to beat out any air bubbles to create a smooth texture.

Ganache

  • Heat the chocolate and heavy cream in the microwave for 30 seconds, stir. Add another 30 seconds and stir again until it's smooth. Add to a squeeze bottle and set aside.

Assembly

  • Fill a piping bag fitted with a large french star piping tip with buttercream, then set aside.
  • With the remaining buttercream, gently spread on a flat layer with an offset icing spatula and smooth it flat with a flat cake scraper.
  • Using a stripe cake scraper with indents, create clean indents in the buttercream. If it doesn't look clean (meaning, clear lines), add on some buttercream in those flawed areas, and scrape again. Clean lines will equal clean stripes, so this step is essential to get right. Be patient, and those lines will appear!
  • Freeze the cake for 15 minutes, until the buttercream is firm. Make the ganache.
  • Pipe in the ganache into the clean indents, and tap the cake flat after each one to spread the ganache into the indent to create a stripe. Repeat with the remaining stripe indents.
  • Pipe line of shells on the two short ends of the cake, then in the center, then between each one so you end up with 5 lines of shell borders.
  • Sprinkle on the chocolate shavings, and enjoy!