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Chocolate Zucchini Cake with Silky Chocolate Frosting
This is the way chocolate cake should be
Rich, chocolaty, super moist and tender is how everyone describes this Chocolate Zucchini Cake. It’s so good you don’t even need the frosting. But please don’t skip the creamy frosting (haha) because it’s so delicious!
Can you tell how much I LOVE this cake? I’ve been working on developing this recipe for several years and finally dialed in the perfect combination of buttery, chocolaty, tender and moist chocolate cake that everyone loves.
Every summer for the past few years I’ve made chocolate zucchini cake for my August birthday. Yes, I make my own birthday cake most years, unless my daughter’s in town and then she’ll make one for me.
If I’m not making Chocolate Zucchini Cake for my birthday then I make my other favorite, Red Velvet. How I love that luscious cream cheese frosting! 😋
Each summer I’ve tweaked this recipe, a little here and a little there, until this year when I nailed it!
Since then I’ve made this recipe into two 9-inch frosted and decorated layers and a 13×9-inch sheet cake. My favorite is the sheet cake version with a little less frosting because the cake is so good.
Nobody can tell there’s zucchini in the cake
You can’t taste the zucchini and it doesn’t make the texture weird or anything. It’s not chewy or dense and it doesn’t look green. It just tastes fantastic and you get vegetables in every bite!
For the chocolate zucchini cake recipe:
- shredded zucchini (do not peel)
- all-purpose flour
- natural unsweetened cocoa powder (not Dutch-process)
- baking soda and baking powder (now’s a good time to make sure they’re still active with this simple test)
- light or dark brown sugar
- granulated sugar
- unsalted butter at room temperature
- vegetable oil or canola oil
- large eggs
- sour cream
- vanilla extract
- espresso powder (optional but highly recommended)
For the chocolate frosting:
- unsalted butter at room temperature
- powdered sugar
- Dutch-process cocoa powder
- heavy cream
- espresso powder (optional)
- vanilla extract
How to make Chocolate Zucchini Cake
1. Preheat the oven and prep the baking pan
If baking in a 13×9-inch baking pan, preheat your oven to 325 degrees F. If you’re baking in two 9-inch round cake pans preheat oven to 350 degrees F. Coat the pans with vegetable cooking spray. You can also line the pan with parchment paper for easy removal to a platter.
NOTE: 9-inch round cake pans must have at least 2-inch high sides.
2. Prepare the zucchini
Grate the zucchini on a large box grater. You can use the large or smaller holes, both work well. Place the shredded zucchini in a fine mesh strainer to drain while preparing the cake batter.
3. Mix the dry ingredients
In a large bowl whisk together the flour, cocoa, salt, baking soda and baking powder. Set aside.
4. Combine the wet ingredients
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.
Next add the sour cream, vanilla and espresso powder. Blend until incorporated.
5. Combine the ingredients
With the mixer speed set on low, add the flour mixture in three additions. Scrape down the sides and bottom of the bowl and blend again until combined.
Fold in the zucchini and pour the batter into the prepared pan. Smooth the top with an off-set spatula.
6. Bake times
Bake at 325 degrees F for 28 to 25 minutes or until a toothpick inserted in the center comes out with no wet batter. Cool completely before frosting. For two 9-inch rounds, bake at 350 degrees F for 25 to 33 minutes.
How to make the creamiest chocolate frosting
PRO TIP: The single most important thing you can do when making homemade frosting is to use the lowest speed of your mixer or blend the ingredients by hand.
Whipping the frosting at high speeds builds in lots of air bubbles which takes away from the desired creamy consistency. Frosting should always be smooth, silky and creamy.
1. Beat the butter
In a large mixing bowl beat the butter on medium-high speed with an electric mixer until creamy and smooth.
2. Sift the dry ingredients
Sift together the powdered sugar and Dutch-process cocoa powder. Add the sifted sugar mixture to the butter along with 3 tablespoons heavy cream, salt, espresso powder and vanilla.
3. Mix on low
Blend the mixture on the lowest setting possible just until combined. Add additional cream, 1/2 tablespoon at a time, until you reach the desired consistency.
If needed, add more sugar for a thicker frosting.
Using a rubber spatula fold the frosting a few times scraping up from the bottom of the bowl until well blended. Don’t over-mix!
4. Frost the cake
Spread the frosting over the cooled cake and serve immediately.
Black Cocoa Powder
For a darker, richer cake with great chocolate flavor, replace 1 tablespoon of natural cocoa powder with black cocoa. I do this in just about all my chocolate recipes that call for cocoa powder.
Black cocoa should be used sparingly to create an intense, dark color with unsweetened-chocolate highlights.
Chopped Dark Chocolate
Turn this cake into a chocolate lovers dream by adding one cup of chopped good quality bar chocolate to the batter before baking. You can also stir in rough-chopped dark chocolate chips or mini chocolate chips.
You can skip the frosting all together and scatter mini chocolate chips over the top before baking. Serve as is or dust with powdered sugar and enjoy.
Add 1/2 to 1 tablespoon of light corn syrup to the frosting along with the heavy cream. Corn syrup gives the frosting a shiny, glossy finish and silky consistency.
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How to store Chocolate Zucchini Cake
For the best flavor, Chocolate Zucchini Cake should be served at room temperature. Leftovers should be stored in the refrigerator, well sealed in an airtight container.
Remove the leftover cake from the refrigerator and allow it to come to room temperature before serving, about 30 to 60 minutes.
Freezing Chocolate Zucchini Cake
This cake is easily frozen before it’s frosted. Simply seal the cold cake in several layers of plastic wrap and then a layer of aluminum foil. Freeze for up to 3 months.
Thaw frozen zucchini cake in the refrigerator then bring to room temperature before serving or frosting.
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Chocolate Zucchini Cake
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
To prepare the cake:
- Preheat oven to 325°F. Spray or grease a 13×9-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 spatular 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.
- 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 13×9-inch cake or about 15 cupcakes. To frost a double layer cake increase the frosting ingredients to 1 1/2 times the original amounts.
Chocolate Zucchini Cake with Creamy Chocolate Frosting
This cake is soft, moist and richly flavored and topped with a memorable chocolate frosting. If you love chocolate, you’re going to love this cake.
Chocolate Zucchini Cake is one of my all-time favorite cakes. It’s not too sweet, the texture is perfect and the flavor is phenomenal. It’s also really easy to make and hard to mess up.
Next time you have an event that calls for chocolate cake, give this recipe a try. You won’t be sorry!
Finally, if you find yourself with a little extra garden fresh zucchini try this Cinnamon Sugar Zucchini Coffee Cake Recipe. Breakfast doesn’t have to be boring!