Chocolate Zucchini Cake

You know those scenes in movies where they lay out the school lunchroom cliques for the new kid? That’s how I used to feel about vegetables in baked goods. Vegetables belong in soup, and chocolate belongs in chocolate cake. Order in the universe, and all that. 

Eventually, I figured if I could make an exception for carrot cake, zucchini deserved a chance. This retro-inspired chocolate zucchini cake is officially the only way I want to eat my greens. It’s extra-moist and indulgent, thanks to sour cream and fresh summer zucchini. And no, you don’t actually taste the veggies!

Why This Chocolate Zucchini Cake Gets an A+

• Heaps of zucchini. There are 3 full cups of shredded zucchini in this cake, but you wouldn’t even know it. You don’t taste or even see the zucchini in this recipe. It’s a silent little helper that makes for an incredibly moist cake. 
• Pourable fudgy frosting. I cover this cake with pourable frosting just like my Sunday chocolate cake. It gives the finished cake irresistible old-school, fudgy brownie vibes, and it’s an easy alternative to frosting and decorating the cake with buttercream.
• Easy to make. I make this as a sheet cake, and it couldn’t be easier. Mix the batter in one bowl and pour it into a 9×13-inch pan to bake. No layers, no fussing. That’s it!

You’ll Need These Ingredients 

Call up your gardener friends (is it just me, or is everyone who grows zucchini always trying to get rid of their zucchini?) and gather the ingredients below. I’ve included some notes and possible substitutions. You’ll find the full printable recipe in the recipe card below the post.

• Butter and Oil – My cake uses both. Butter for richness and flavor, and oil for that extra-moist, tender texture. You can use any neutral-flavored vegetable oil, like canola.
• Dry Ingredients – All-purpose flour, granulated sugar, baking soda, baking powder, and salt. Remember to check the expiration dates on your baking soda/powder to make sure it’s fresh.
• Eggs and Vanilla – If you think of it, take your eggs out of the fridge ahead of time so they can come to room temperature.
• Sour Cream – If you’ve ever made my sour cream chocolate cake, you already know that sour cream is the secret to a super-moist, flavorful cake. If you don’t have sour cream, use Greek yogurt instead.
• Cocoa Powder – Since this cake contains baking soda, you’ll want to use natural, unsweetened cocoa powder.
• Zucchini – Freshly grated (a box grater works perfectly for this). Look for firm, green zucchini without any blemishes. No need to peel it before you shred it. 
• Chocolate Chips – I use semisweet chocolate chips, but dark chocolate, milk chocolate, or even white chocolate chips will also work.

For the Icing

• Butter – Salted or unsalted.
• Milk – This can be whole milk, 2%, or any kind you’d prefer.
• Cocoa Powder – You can use the same cocoa powder that you used for the cake.
• Powdered Sugar – Also called confectioner’s sugar or icing sugar. If you’d like, sift the powdered sugar for a perfectly smooth frosting that’s free from lumps.

How to Make Chocolate Zucchini Cake

This chocolate zucchini cake recipe comes together just as easily as my chocolate chip zucchini bread. All you need is one bowl and a baking dish. Have a quick look at the overview below, and scroll to the recipe card for the printable instructions.

1. Mix the wet batter. To begin, beat softened butter with oil and sugar until it’s smooth and fluffy. Then, add in the vanilla, followed by the baking soda, baking powder, salt, and eggs. Scrape down the sides of the bowl while you stir.
2. Add the remaining ingredients. Next, alternate adding the flour with the sour cream, stirring in between. Stir in the cocoa powder, then fold in the zucchini and chocolate chips.
3. Bake. Pour the cake batter into a greased 9×13-inch baking pan. Bake at 325ºF for 30-40 minutes, until a toothpick stuck into the middle of the cake comes out clean (a few moist crumbs are fine, though).

Pourable Chocolate Icing (a.k.a. The Best Frosting for Zucchini Cake!)

This is similar to the fudgy boiled frosting that you’d pour over a batch of brownies or a Texas sheet cake. It’s literally the icing on the cake! If you’d prefer a vanilla frosting, you can top this zucchini cake with classic vanilla buttercream or my old-fashioned heritage frosting. It’s delicious either way. The main perk of this chocolate icing is that you don’t need a mixer! These are the steps to make it:

1. Heat the ingredients. First, combine melted butter with milk and cocoa powder in a saucepan over medium-low heat. 
2. Add powdered sugar. Stir while the butter melts, then take the pan off the heat and whisk in the powdered sugar. Keep whisking until no lumps are left.
3. Frost the cake. While the cake is still warm from the oven, pour the prepared icing generously over the cake and spread it evenly. Afterward, cool the cake before serving.

Frequently Asked Questions

Should I Peel the Zucchini?

Peeling is optional, but I don’t bother! Just give the zucchini a good wash and dry it before passing it over the box grater. Finely grate it for the best texture (we want to avoid big chunks of zucchini at all costs).

Do I Need to Drain the Shredded Zucchini?

Some recipes call for draining or squeezing the liquid out of the shredded zucchini before adding it to the cake batter, but not this one. I created this recipe so that the moisture from the zucchini works with the other ingredients to make an ultra-moist cake. If you find that your zucchini is particularly mushy or watery, you can blot it lightly with a paper towel, but I don’t recommend more than that.

Can I Make Cupcakes Instead?

Absolutely! This recipe makes enough batter for 24 cupcakes that are just as fudgy and delicious as my classic chocolate cupcakes. Bake the batter in a lined standard cupcake tin at 350ºF for about 20 minutes. I recommend pairing your chocolate zucchini cupcakes with my easy chocolate buttercream.

Tips and Variations

• Use room-temperature ingredients. Take your butter, sour cream, and eggs out of the fridge 30 minutes ahead of when you’ll make your cake. Room-temperature ingredients blend more smoothly into the batter.
• Don’t overmix the cake batter. The cardinal rule of baked goods! Don’t overmix. Too much mixing after the flour is added can overdevelop the gluten, leading to a dense, tough cake.
• Measure the dry ingredients correctly. When measuring out the flour, use the spoon and sweep method. Spoon the flour from the bag and into the measuring cup (don’t scoop from the bag). Afterward, level off the flour with the back of a knife for a nice, level cup of flour. Overmeasuring can lead to a dry cake.
• Frost the cake while it’s warm. Unlike other cake recipes, where you need to wait for the cake to cool completely before you frost it, this cake is meant to be frosted shortly after baking. Pour the icing over the cake when it’s still a bit warm (but not hot) from the oven.
• Deepen the flavor. Add a small amount (1 tablespoon) of espresso powder to the cake batter. Just like the zucchini, you won’t taste the coffee, but it helps to enrich the flavor of chocolate cakes.