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A slice of two layer chocolate cake on a white plate with a fork and a bite taken out

Double Chocolate Layer Cake (Chocolate Mayonnaise Cake)

5 from 1 vote
This is my favorite chocolate cake recipe because it's easy to make, ready in under an hour, and reminds me of the famous Portillo's chocolate cake from Chicago! You might know this as "chocolate mayonnaise cake" - a moist chocolate cake, rich and chocolatey, covered in a thick layer of chocolate buttercream frosting, and layered for a decadent dessert. The perfect base for my homemade Portillo's Chocolate Cake Shake.
Prep Time 15 minutes
Cook Time 30 minutes
Total Time 1 hour 15 minutes
Servings 8 to 16 slices, depending on size

Ingredients
  

Chocolate Cake

  • 1 box, 15.25 ounces Betty Crocker Super Moist Milk Chocolate cake mix
  • 3 large eggs, room temperature
  • 1 cup water
  • 1 cup mayonnaise

Chocolate Frosting

  • 10 ounces semisweet, milk, or dark chocolate chips
  • 1 ½ cups unsalted butter, room temperature
  • 3 cups powdered sugar
  • 1 Tablespoon vanilla extract

Instructions
 

Chocolate Cake

  • Preheat oven to 350°F. Spray two round cake pans with non-stick spray and set aside.
  • In a large bowl, combine cake mix, eggs, water and mayonnaise and beat with a hand or stand mixer on medium speed until well combined.
  • Pour half of the batter into each of the prepared pans, and bake for 25-30 minutes or until a toothpick inserted into the center comes out with moist crumbs. 
  • Let cool in pans for 5 minutes, then carefully remove from pans and transfer to wire racks to cool completely.
  • Once cooled, level off the top of one of the cakes (this will be your bottom layer). You can also level off both if you'd like the top to be flat as well. Set aside the pieces you've shaved off the tops and set aside.

Chocolate Frosting

  • In a double broiler or in the microwave, melt chocolate until smooth and set aside to cool.
  • In a large bowl, beat butter with a stand mixer or hand mixer until smooth.
  • Add powdered sugar and beat until well combined, starting on low speed and increasing as the powdered sugar incorporates.
  • Add vanilla extract and melted chocolate, and beat until well combined and smooth.
  • Place the leveled off cake layer on a platter and frost the top with ⅓ of the prepared frosting. Top with second cake layer and frost the top and sides of both layers with remaining frosting.

Notes

Storage:
  • If you're storing the assembled, frosted cake you'll want to cover the leftover cake tightly and store in the refrigerator for 5-6 days. I emphasize the "tightly" because you don't want cold air from the fridge to suck moisture out of it.
  • If you're storing the baked and cooled cake layers before frosting, wrap each cake layer individually in plastic wrap and foil (and in a freezer-safe container) and freeze for up to 3 months. Bring them to room temperature before assembling and frosting.
  • As for the frosting, you can make this up to 3 days ahead of time and store in an airtight container in the fridge. You may just need to get it a quick re-whip before using.
Nutrition: The nutritional information below is for 8 slices - divide in half for 16 slices.

Nutrition

Calories: 1135kcal | Carbohydrates: 103g | Protein: 8g | Fat: 79g | Saturated Fat: 35g | Polyunsaturated Fat: 17g | Monounsaturated Fat: 22g | Trans Fat: 1g | Cholesterol: 167mg | Sodium: 657mg | Potassium: 421mg | Fiber: 4g | Sugar: 79g | Vitamin A: 1190IU | Calcium: 126mg | Iron: 5mg
Course Dessert
Cuisine American
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