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A chocolate zucchini cake with a slice removed with a small vase of flowers behind it.
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Chocolate Zucchini Cake

A three-layer chocolate zucchini cake packed with hidden grated zucchini, semi-sweet chocolate chips folded into the batter, and a silky chocolate buttercream made with melted chocolate ganache. The zucchini disappears into the crumb completely—what's left is the fudgiest, most decadent chocolate cake in my repertoire.
Course Dessert
Cuisine American
Prep Time 30 minutes
Cook Time 35 minutes
Total Time 1 hour 5 minutes
Servings 12 servings
Calories 1285kcal
Author John Kanell

Equipment

  • Stand mixer
  • Three 8 inch cake pans

Ingredients

For the Cake:

  • 3 cups all-purpose flour (360g)
  • 1 cup unsweetened natural cocoa powder (100g)
  • 1 tablespoon baking soda
  • ¾ teaspoon baking powder
  • 1 ½ teaspoons espresso powder optional
  • ¾ teaspoon salt
  • 1 ½ cups vegetable oil (354ml)
  • 1 ½ cups granulated sugar (300g)
  • 1 cup light brown sugar packed (220g)
  • 6 large eggs room temperature
  • ½ cup sour cream room temperature (120g)
  • 1 tablespoon vanilla extract
  • 4 ½ cups grated zucchini (about 3 medium zucchini) (475g)
  • 1 ½ cups semi sweet chocolate chips (270g)

For the Buttercream:

  • 1 cup semi sweet chocolate chips (180g)
  • ⅔ cup heavy cream divided, (160ml)
  • 5 ½ cups powdered sugar (660g)
  • 1 ½ cups unsalted butter room temperature (282g)
  • ½ teaspoon salt
  • ⅓ cup unsweetened natural cocoa powder (33g)
  • 1 ½ teaspoons vanilla extract

Instructions

For the Cake:

  • Preheat the oven to 350ºF and grease three 8-inch cake pans with baking spray or butter and flour. Line the bottom with a parchment round, and wrap them with fabric soaked baking strips, if you have them.
  • In a large bowl whisk together the flour, cocoa powder, baking soda, baking powder, espresso powder, and salt. Set aside.
  • In another large bowl combine the vegetable oil, granulated sugar, brown sugar, eggs, sour cream and vanilla and whisk until smooth. With a spatula, fold the zucchini into the wet ingredients until fully incorporated.
  • Pour the wet ingredients into the dry and stir until almost combined (there should be a few dry streaks remaining). Add in the chocolate chips and stir in until no dry streaks remain and the chocolate is well dispersed throughout the batter.
  • Divide the batter evenly among the cake pans (about 3⅓ cups/810g each). Bake for 35 to 40 minutes or until the centers are springy to the touch and the cakes start to pull away from the sides of the pans. Allow the cakes to cool in the pan for 10 minutes before inverting onto a wire rack to cool completely. Remove the parchment paper once cooled.

For the Buttercream:

  • Place the chocolate chips and ⅓ cup of the heavy cream in a small microwave safe bowl or a liquid measuring cup. Microwave in 30 second intervals, stirring between each, until the chocolate is fully melted. Set aside to cool while you make the frosting.
  • In the bowl of a stand mixer fitted with a paddle attachment, cream the butter and salt on medium speed until light and creamy, about 3 minutes. Sift in the cocoa powder and mix on low until combined. Scrape down the bowl.
  • While mixing on low, gradually add the powdered sugar, about 1 cup at a time, alternating with a small pour of the remaining ⅓ cup of heavy cream. Once all of the powdered sugar and cream is incorporated, add in the vanilla extract and melted cooled chocolate.
  • Increase the mixer to medium speed and beat for 2 minutes or until the buttercream is very light, fluffy, and easy to spread. Transfer 1 cup (236g) of the frosting to a piping bag fitted with an open star tip (Ateco 869.)

For the Assembly:

  • Place a cooled cake layer on a cake stand or serving plate and top with 1 cup of buttercream, spreading into an even layer all the way to the edge. Top with another cake layer and repeat with the buttercream. Top with the remaining cake layer, placing it top side down so the top of the cake is even. Spread the remaining buttercream all over the top and sides of the cake. I prefer to leave a thicker layer on top, and spread a thinner layer on the sides, then use an offset or bench scraper to remove most of the frosting on the sides. This gives the cake a naked cake look and a perfect balance of frosting to cake.
  • Finish decorating the cake by piping dollops of buttercream around the top edge of the cake. For clean slices, chill the cake for at least 30 minutes before slicing so the frosting firms up a bit and the cake is easier to slice.

Notes

  • Chill the cake before slicing. This firms up the frosting enough to make the cake stable to cut cleanly. A quick 30 minute chill will do the trick!
  • Making this for a party? Use my technique for cutting a round cake to get more servings out of the cake to feed a crowd.

Nutrition

Calories: 1285kcal | Carbohydrates: 150g | Protein: 12g | Fat: 75g | Saturated Fat: 33g | Polyunsaturated Fat: 18g | Monounsaturated Fat: 19g | Trans Fat: 1g | Cholesterol: 166mg | Sodium: 600mg | Potassium: 607mg | Fiber: 8g | Sugar: 113g | Vitamin A: 1194IU | Vitamin C: 8mg | Calcium: 116mg | Iron: 6mg