Rich, fudgy, and unbelievably moist, this double chocolate zucchini cake is the ultimate crowd-pleasing dessert. Quick to make with simple ingredients—no mixer needed—and no one will guess it’s packed with hidden veggies!
Every summer, I seem to have more zucchini than I know what to do with, thanks to my mother-in-law’s abundant garden. So, I find myself getting creative in the kitchen with recipes like my zucchini ricotta tart.
However, my absolute favorite way to put the veggie to use is in this chocolate zucchini cake!
Why you’ll love this recipe
- Rich and flavorful – The cake itself is ultra chocolatey with a tangy sour cream frosting that balances the sweetness nicely.
- Moist and soft– The use of fresh zucchini and brown sugar creates a soft, fluffy cake with the perfect amount of moisture.
- Quick and easy – With no hand mixer or fancy equipment required, this cake comes together with simple steps and is virtually foolproof.
With 24 servings, this zucchini cake makes plenty to feed a crowd, but my family is known to enjoy the entire thing ourselves in just a few days!
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Pin ItKey Ingredient Notes
- All-purpose flour forms the base of the cake batter. I haven’t tested this recipe with a gluten-free flour, but it should work if you use a 1:1 all-purpose gluten-free flour blend! Take a look at my notes on different types of flour before making any substitutions.
- Cocoa powder – I use unsweetened natural cocoa powder. Although similar in many ways, Dutch process and natural cocoa powder are not interchangeable in this recipe!
- Light brown sugar – A common type of sugar in baked goods, this is my secret to a sweet, super moist cake with lots of depth.
- Zucchini – You’ll need 3 cups of grated zucchini for this recipe, which equals about one pound of fresh zucchini.
- Chocolate chips – I prefer chopped semi-sweet chocolate or chocolate chips for this recipe, but dark chocolate or milk chocolate also work, if preferred.
- Sour cream – This forms the base of the frosting, creating a light, fluffy texture.
Skip wringing the zucchini
Many chocolate zucchini cake recipes require you to wring out all the moisture from the zucchini. However, I don’t find it necessary. Not only does this eliminate a pretty time-consuming step, but the moisture also contributes to the soft batter.
How to make chocolate zucchini sheet cake
Before you begin, preheat your oven to 350°F, and grease a 9×13-inch baking pan with cooking spray.
1. Prepare the Cake Batter
- Whisk the dry ingredients in a large bowl.
- Whisk the wet ingredients in a second larger bowl until smooth.
- Pour the wet ingredients into the bowl of dry ingredients, and fold until the batter is mostly incorporated. It’s okay if there are still a few small lumps!
- Stir in the grated zucchini.
- Add the chopped chocolate and stir to combine. Be careful not to stir too long! We don’t want to overwork the batter.
2. Bake
- Pour the cake batter into the prepared baking pan.
- Bake until a toothpick inserted into the center comes out clean. This typically takes about 25-30 minutes, but may vary slightly depending on your oven.
- Cool in the pan slightly, and transfer the cake to a wire rack to cool completely.
3. Make the Frosting
- Mix the sour cream, powdered sugar, and vanilla in a bowl until smooth. I just use a spoon for this!
5. Frost the cake and serve
- Smear the frosting all over the cooled cake.
- Slice the zucchini cake into squares and enjoy!
Tips for Success
- Measure the flour correctly! I highly recommend using a scale to measure the dry ingredients, especially flour. It’s really easy to over-measure flour by volume, which will lead to a dense and heavy cake. If you don’t have a scale, instead of scooping the flour with a measuring cup, spoon the flour into a measuring cup and then level the top off with the back of a knife. This is called “spoon and level” method. Don’t be tempted to shake the measuring cup or pack the flour down!
- Don’t overmix the batter. Mix just until the batter is smooth and no large lumps remain. Continuing to stir will overwork the gluten in the flour, creating a dense, tough cake.
- Don’t overbake the cake. This is the most common mistake when it comes to dry cakes. Overbaking dries out cake batter, and there’s no fix for it!
- Cool the cake completely. The cake will continue to cook and set as it cools, preventing sinking. In addition, if you frost the cake while it’s warm, the frosting is likely to slide right off!
Storing Tips
You can make this double chocolate zucchini cake up to a day in advance and store it in the fridge.
- Store the frosted cake tightly covered in the fridge for up to 5 days. Bring the cake back to room temperature when you’re ready to eat.
- Freeze unfrosted cake for up to 3 months! Thaw in the fridge overnight, and add the frosting just before serving.
FAQs
There’s no need! The pieces are so small that no one notices them. However, if you prefer an even smoother texture, you can peel the zucchini, if desired.
The most common reasons for a cake sinking are using an incorrect oven temperature, having too much moisture, and overmixing the batter. Make sure to allow plenty of time for your oven to heat, measure your ingredients carefully, and stir just until the batter is combined!
I don’t recommend it! I’ve tested this recipe with cream cheese frosting and find it way too heavy. Sour cream frosting is light and fluffy, which prevents the cake from sinking.
More Sheet Cake Recipes
Double Chocolate Zucchini Sheet Cake
Ingredients
For cake:
- 1 ½ cups (190 g) all-purpose flour
- ¾ cup (60 g) unsweetened natural cocoa powder
- 1/3 cup (65 g) light brown sugar
- 1 teaspoon baking powder
- ½ teaspoon baking soda
- ½ teaspoon coarse kosher salt or ¼ teaspoon table salt
- 1 can (400 g) sweetened condensed milk
- 2 large eggs at room temperature
- ½ cup (113 g) unsalted butter melted and cooled
- 1 teaspoon pure vanilla extract
- 3 cups grated zucchini Note 1
- 4 oz (115 g) semi-sweet chocolate chopped Note 2
For frosting:
- 1 ½ cups (360 ml) sour cream
- ¼ cup (32 g) powdered sugar
- 1 teaspoon pure vanilla extract
Instructions
- Preheat the oven to 350°F (177°C). Spray 9×13-inch (23x33cm) baking pan with a cooking spray.
- In a large bowl, whisk together flour, cocoa powder, brown sugar, baking powder, baking soda and salt.
- In a medium bowl, whisk sweetened condensed milk, eggs, butter and vanilla extract until smooth.
- Pour the wet ingredients into the dry ingredients and fold the batter with a silicone spatula until mostly incorporated.
- Stir in grated zucchini.
- Add chopped chocolate and give it a good stir. Don’t mix for too long.
- Pour the batter into the prepared baking pan.
- Bake for 25-30 minutes, or until inserted toothpick comes out clean.
- Transfer to wire rack and cool completely.
- To make the frosting, mix sour cream with powdered sugar and vanilla extract until smooth.
- Once the cake is cooled completely, smear the frosting and cut into small squares.
- The cake can be made a day in advance. Store the frosted cake in the fridge, tightly covered. The cake is best served at room temperature. Leftovers are good for up to 5 days, covered and refrigerated.
⭐️ Did you make this recipe?
Please leave a review and let us know how you liked it!
Tips & Notes
– Store the frosted cake tightly covered in the fridge for up to 5 days. Bring the cake back to room temperature when you’re ready to eat.
– Freeze unfrosted cake for up to 3 months! Thaw in the fridge overnight and add the frosting just before serving.
Nutrition
This recipe was originally published on September 6, 2016.
This is simple to make and turned out great. The photos are very helpful since I like to verify the batter “looks right.”
So glad you tried and loved the recipe, Emme!! Thank you for your feedback!!!
Question: It is called SHEET cake… usually sheet cake is made in a jelly roll pan…. has anyone doubled this for a sheet cake size?
You don’t need to double the recipe. Just use jelly roll pan instead of 9×13-inch pan.
I have a recipe for chocolate zucchini cupcakes that I make all the time. The zucchini makes the cake so wonderful and moist. I love this sheet cake version and the addition of the sour cream frosting!
Mmm, chocolate zucchini cupcakes sound really good! You’ll love this sheet cake too, Kim. Hope you give it a try.
This cake looks awesome- no doubt why it would be a crowd pleaser 🙂 And I love the sour cream in the frosting!
Sour cream frosting is so good! Thanks for stopping by, Medha!