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Overhead of a chocolate sheet cake cut into squares with one piece removed
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5 from 12 votes

Chocolate Zucchini Cake

Soft, moist and richly flavored Chocolate Zucchini Cake topped with a memorable chocolate frosting. This cake is one of my all-time favorites!
Prep Time45 minutes
Cook Time35 minutes
cooling11 hour
Total Time2 hours 20 minutes
Course: Dessert
Cuisine: American
Keyword: cake, chocolate, dessert
Servings: 20
Calories: 401kcal
Author: Tricia

Ingredients

For the cake:

  • 2 cups shredded zucchini about 1 medium 9oz squash (do not peel)
  • 2 ¼ cups all-purpose flour (284g)
  • ¾ cup unsweetened natural cocoa powder (78g) not Dutch-process
  • 1 teaspoon salt
  • 1 teaspoon baking soda
  • ½ teaspoon baking powder
  • 1 cup light brown sugar packed (226g)
  • ¾ cup granulated sugar (170g)
  • 8 tablespoons unsalted butter at room temperature (½ cup, 113g or 4oz)
  • ½ cup vegetable or canola oil (4oz)
  • 4 large eggs room temperature
  • 1 cup sour cream (8oz)
  • 2 teaspoons vanilla extract
  • ¼ teaspoon espresso powder

For the frosting:

  • 12 tablespoons unsalted butter at room temperature (6oz or ¾ cup)
  • 3 cups powdered sugar 384g
  • ½ cup Dutch-process cocoa powder
  • 3 to 5 tablespoons heavy cream or milk
  • ¼ teaspoon salt
  • pinch of espresso powder optional
  • 1 ½ teaspoons vanilla extract

Instructions

To prepare the cake:

  • Preheat oven to 325°F. Spray or grease a 13x9-inch baking pan. If desired line the pan with a piece of parchment paper large enough so the excess hangs over the sides for easy removal. Or skip the parchment and cut the cake in the pan.
  • Grate the unpeeled zucchini on a large box grater (large or smaller holes both work) and place in a fine mesh strainer over the sink to drain while preparing the cake batter.
  • In a large bowl whisk together the flour, cocoa, salt, baking soda and baking powder. Set aside.
  • In another large bowl combine the sugars, butter and oil. Beat with an electric mixer until lightened and creamy. Add the eggs, one at a time, beating just until the yolks disappear. Scrape down the sides and bottom of the bowl with a rubber spatula. Add the sour cream, vanilla and espresso powder and blend just until incorporated.
  • With the speed on low, add the flour mixture in three additions. Scrape down the sides and bottom of the bowl and blend again until combined.
  • Gently blot the top of the shredded zucchini with dry paper towels. Don’t press down or remove too much moisture. The zucchini should be very moist but not wet. Add the shredded zucchini to the batter. Fold together with a spatula until blended. Pour the batter into the prepared cake pan and smooth the top.
  • Bake at 325°F for 28 - 35 minutes or until a toothpick inserted in the center comes out clean. Moist crumbs are okay but no wet batter. Cool the cake completely before frosting.

To prepare the frosting:

  • In a large bowl beat the butter on medium-high with an electric mixer until creamy and smooth.
  • Sift together the powdered sugar and Dutch-process cocoa powder. Add the sugar mixture to the beaten butter along with 3 tablespoons heavy cream, salt, espresso powder and vanilla. Blend on the lowest possible setting just until combined. You can also mix by hand with a wooden spoon.
  • Add additional heavy cream, 1/2 tablespoon at a time, until you reach the desired consistency. If needed add more sugar for a thicker frosting.
  • Fold the frosting a few times with a rubber spatula scraping up from the bottom of the bowl. Don’t over-whip or over-mix the frosting as that will create air bubbles and the frosting won’t be as smooth, silky and creamy.
  • Spread the frosting over the cooled cake. Serve immediately.

Notes

  • For a rich, darker chocolate cake replace 1 tablespoon of the cocoa powder with black cocoa.
  • This cake can also be made in two 9-inch round cake pans with 2-inch high sides. Bake at 350 degrees F for 25 to 33 minutes.
  • 1 cup of chopped bar chocolate, rough chopped dark chocolate chips, or mini chocolate chips can be added to the batter before baking.
  • In place of the icing sprinkle the top with 1 cup mini chocolate chips before baking. Dust with powdered sugar and serve.
  • Store leftover cake well sealed in the refrigerator. Set out at room temperature for 1 hour before serving for the best flavor.
  • Frosting can be made several days in advance. Cover and refrigerate until needed. Remove from the refrigerator 30 minutes before using. Add a little more milk or cream to the frosting if needed to reach desired consistency.
  • Add 1 tablespoon light corn syrup to the frosting if desired for a silky, almost glossy finish.
  • This amount of frosting is enough to cover a 13x9-inch cake or about 15 cupcakes. To frost a double layer cake increase the frosting ingredients to 1 1/2 times the original amounts.

Nutrition

Calories: 401kcal | Carbohydrates: 51g | Protein: 4g | Fat: 22g | Saturated Fat: 10g | Polyunsaturated Fat: 2g | Monounsaturated Fat: 8g | Trans Fat: 0.5g | Cholesterol: 72mg | Sodium: 235mg | Potassium: 178mg | Fiber: 2g | Sugar: 37g | Vitamin A: 527IU | Vitamin C: 2mg | Calcium: 48mg | Iron: 2mg