Chocolate Zucchini Cake

Chocolate Zucchini Cake

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Since I keep getting zucchini in my CSA, I knew I had to revisit this chocolate zucchini cake recipe.

Amelia usually won’t eat zucchini, and there’s only so much zucchini that Alex and I can eat (although it is great grilled). So savory dishes were out for a little while.

I’m not much of one to hide vegetables in food; kids (and adults) need to know what they’re eating, and I want my daughter to grow up to enjoy vegetables. But when you’re faced with more zucchini than you can eat for dinner, you do what you have to do.

three plates of chocolate zucchini cake

I first made this cake in 2010, as recipe #185 of my 365 recipe challenge. I had a zucchini plant then that kept prolifically producing giant zucchini. I had to become creative about how I used it, since I can’t waste food. So I was thrilled when I came across this recipe.

9 years later, I’m so glad I remembered this fantastic cake. It’s one of the richest, most chocolatey cakes you can make. The zucchini just disappears into it, keeping it moist (with some help from butter, oil, and a little yogurt).

It’s so dense it’s almost brownie-like in texture. A simple glaze from chocolate chips gilds the top. Best of all, the cake is very easy to make.

chocolate zucchini cake, on a plate
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First, let’s talk ingredients. The cake takes both butter (for richness) and oil (for moisture). That said, I think you could use only one if you wanted to.

I love that it’s a chocolate cake made from cocoa powder, which is inexpensive and shelf-stable. I don’t like melting chocolate and stirring it in.

I usually use yogurt in my recipes instead of buttermilk or sour cream, but use whatever you have. You can also substitute sour milk by mixing together 1 1/2 teaspoons of vinegar or lemon juice with just under 1/2 cup of milk. (Any kind of non-dairy milk should work fine as well.)

The cake takes 3 cups of shredded zucchini, which can weigh different amounts, depending on the size and water content of the zucchini. I’ve weighed mine, and if I pat it down into my measuring cup, it usually weighs 400 grams (about 14 ounces). This moisture content can affect how long the cake bakes.

chocolate zucchini cake, on plates, with the pan along the side

How finely should I shred my zucchini? I’ve made this with both coarsely and finely shredded zucchini. Both work fine. A food processor makes this fast and easy. (I love my Breville food processor (affiliate link).) You can also have it grated. DO NOT puree it, as that will make the batter too liquidy.

Chocolate chips go into the cake, and also make up the simple icing on top. I use semisweet, but I bet milk chocolate would be good too. I often use Ghirardelli chocolate chips (affiliate link), but store-brand and Aldi brand work just as deliciously in this cake.

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How to Make the Cake

I’ve adapted this cake from the King Arthur Flour website, and I like to think I’ve made it a tiny bit easier.

It’s a straightforward, easy-to-make cake batter to make. Beat together butter, oil, sugar, vanilla, and leavenings with an electric mixer until relatively smooth (the sugar will partially dissolve), then add the eggs.

butter and oil creamed with sugar and other ingredients until smooth
Butter, oil, and sugar creamed until smooth, before adding eggs

On low speed, add half the flour and cocoa. Add yogurt (or buttermilk or sour cream), then stir in the remaining flour and cocoa. Stir in shredded zucchini and a few chocolate chips, then bake. The liquid in the zucchini will loosen up the batter, making it easier to spread in the pan.

Your baking time will depend in part on how much moisture is in your zucchini. It also varies a little with your pan. I use a greased, shiny natural aluminum 9×13-inch pan (affiliate link) that I love; the cake will likely bake more quickly in a glass or dark metal pan.

batter for chocolate zucchini cake, in a metal pan

You have two options for testing for doneness.

For a more dense, brownie-like cake, pull the cake out when the top springs back when you touch it. Top with your reserved chocolate chips, then bake until a toothpick comes out clean (or nearly clean – a few crumbs are fine). Then spread out the melted chocolate chips. (All pictures were taken with this brownie-like cake; you can see that the top isn’t fully domed.)

The cake flattens out a little from the weight of the chocolate chips, which makes it more dense. Since it’s more dense, you may have to bake it for longer than 5 minutes to get it to be done since the cake loses some heat when you remove it from the oven. Of course, how long it takes depends on the amount of moisture in the zucchini.

baked cake, with heated chocolate chips on top
Softened chocolate chips on top of a dense, brownie-like chocolate zucchini cake baked until the top springs back

Second option: for a traditional cake, bake it until a toothpick inserted in the center comes out clean (or with a single crumb or two). Top with chocolate chips, return it to the oven for just 1 minute, then spread out the melted chocolate chips.

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How to Store Chocolate Zucchini Cake

I usually leave my cakes in a covered container at room temperature. That’s fine for this cake for about 3 days. However, this is such a moist cake that I recommend storing it in the fridge if it’ll take you longer than that to eat it.

This springy, delicious cake is moist, rich, and satisfying. It’s delicious both warm out of the oven and at room temperature. I think it would be perfect served with a glass of milk.

If you like rich chocolate cake, you should make this recipe. Just be sure that it’s done enough before you put the chocolate chips on it so that the edges don’t overbake.

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chocolate zucchini cake, on a plate, with another slice in the background

Want something else sweet to do with zucchini? Try Chocolate Zucchini Bread or classic Zucchini Bread. I’d love to hear over zucchini ideas in the comments below.

Interested in other recipes? I save and share recipes I like or want to try on my Pinterest page – follow me there! You can also check out my Facebook page for more recipes and helpful tips. I’m also happy to try to help troubleshoot my recipes there.

Have you tried this recipe? Or have a question about it? Rate it or leave a comment below! (PS: rating my recipes helps other people find them too!)

In the past:

One Year Ago: Fennel Spice Rub

Two Years Ago: Confetti Cake

Three Years Ago: Whole Wheat Molasses Bread, Sprinkle Cookies

Five Years Ago: Poolish Baguettes, Vanilla Chai Donuts

Six Years Ago: Alton Brown Asian Slaw

Seven Years Ago: Date, Rum, and Pecan Ice Cream

Nine Years Ago: Blueberry Cinnamon Swirl Ice Cream, Chocolate Zucchini Bread

Chocolate Zucchini Cake
Prep Time
30 mins
Cook Time
45 mins
Total Time
1 hr 15 mins

This springy, rich chocolate cake has zucchini hidden inside. The zucchini is undetectable but keeps the cake incredibly moist!

Course: Dessert
Cuisine: American
Keyword: chocolate zucchini cake
Servings: 20
Calories: 306 kcal
Author: Leona Konkel
  • 3 cups shredded zucchini (~400 grams; about one 10" zucchini, just under a pound)
  • 1/2 cup butter (112 grams) (softened)
  • 1/2 cup vegetable oil (112 grams)
  • 1 3/4 cups sugar (336 grams)
  • 1 teaspoon vanilla
  • 1 teaspoon baking soda
  • 1/2 teaspoon baking powder
  • 1/2 teaspoon salt
  • 2 eggs
  • 1/2 cup yogurt, sour cream, or buttermilk (113 grams)
  • 2 1/2 cups flour (300 grams)
  • 3/4 cup cocoa (60 grams)
  • 1/2 cup chocolate chips (85 grams)
  • 1 cup chocolate chips (170 grams)
  1. Shred or grate your zucchini if you haven't already. I leave the skins on mine. Both finely and coarsely grated zucchini work fine; just don't puree it.

  2. With an electric or stand mixer, combine butter, oil, sugar, vanilla, baking soda, baking powder, and salt, mixing until smooth.(The sugar will begin to dissolve.) Add eggs.

  3. Sift together your flour and cocoa powder if you're worried about lumps. Add half of the flour and cocoa, then the yogurt, and then the rest of the flour and cocoa, mixing until just combined. Stir in shredded zucchini and 1/2 cup of the chocolate chips.

  4. Pour into a greased 9×13-inch pan. Bake at 325F for 30-35 minutes before testing the cake for doneness. (See instructions below, and notes.)

  5. Option 1, for a denser cake: Bake until the top of the cake springs back when touched. The center will be set, and a toothpick inserted into the center will have some dense crumbs (like with brownies). Top the cake immediately with 1 cup of chocolate chips. Return the cake to the oven for at least 5 minutes, and bake until a toothpick inserted into the center comes out clean.

  6. Option 2, for a more traditional cake: Bake until a toothpick inserted into the cake comes out clean (or nearly clean, with just a few crumbs). Top immediately with 1 cup chocolate chips, then return the cake to the oven for 1 minute to soften the chocolate chips.

  7. Remove cake from oven. Immediately smooth out hot chocolate chips into a glaze. Cool at least 10 minutes before serving. You can store it covered at room temperature for up to 3 days, but storing in the refrigerator is recommended.

Recipe Notes

The baking time for this cake will vary depending on the amount of moisture in your zucchini. Last time I baked it, I used a larger, late-season zucchini, and it took 42 minutes for a toothpick to come out almost clean (for a traditional cake, Option 2) before adding the chocolate chips. If you add the chocolate chips too soon, it may take up to 50 minutes to finish the cake.

Hack together sour milk to substitute for the yogurt by adding 1 1/2 teaspoons vinegar to just under 1/2 cup of milk. 

I believe you could swap a third of the all-purpose flour for whole wheat flour without noticing a difference in taste or texture. 

This recipe was adapted from King Arthur Flour.

[This recipe was originally published August 9, 2010. Updated in 2019 with updated photos, text, and recipe.]

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