Name: Chocolate Mayonnaise Sheet Cake Recipe
Prep time: 20 min
Cook time: 30 min
Total time: 1 h 20 min
Cuisine: American
Ingredients: Butter, for greasing the pan; 2 cups (242g) all-purpose flour; 1 cup (120g) unsweetened Dutch processed cocoa powder; 1 1/2 teaspoons baking powder; 1 1/2 teaspoons baking soda; 1/4 teaspoon salt; 3/4 cup (177ml) hot water; 2 tablespoons (30g) instant coffee powder or instant espresso powder; 2 large eggs; 1 cup (220g) sugar; 1/2 cup (100g) brown sugar, lightly packed; 1 cup (260g) mayonnaise; 1 tablespoon vanilla extract; 1/2 cup (80g) finely chopped semisweet or bittersweet chocolate; 1/2 cup (113g) unsalted butter; 2 tablespoons (30g) unsweetened Dutch processed cocoa powder; 1 cup (130g) powdered sugar; 1/2 cup heavy cream

There’s something so ridiculously satisfying about a rich, moist chocolate cake that uses an unexpected star ingredient — and this one is no exception. Let me introduce you to the magic of the Chocolate Mayonnaise Sheet Cake Recipe. Trust me, once you try it, you’ll be hooked on how tender and unbelievably fudgy it turns out every time.

A glass tray holds a rich, dark brown cake with a thick, smooth layer of lighter brown frosting on top that has soft swirls and peaks. Three square pieces have been cut from the cake, showing the dense, moist texture of the dark cake underneath the glossy, creamy frosting. The cake sits on a white marbled surface with some crumbs around the tray edges. photo taken with an iphone --ar 2:3 --v 7

Jump to:

Why You'll Love This Recipe
Ingredients & Why They Work
Make It Your Way
Step-by-Step: How I Make Chocolate Mayonnaise Sheet Cake Recipe
Top Tip
How to Serve Chocolate Mayonnaise Sheet Cake Recipe
Make Ahead and Storage
Frequently Asked Questions:
Final Thoughts
Chocolate Mayonnaise Sheet Cake Recipe

Why You'll Love This Recipe

This cake has quietly become one of my go-to chocolate desserts because it’s not just easy—it’s uniquely delicious in a way that really surprises guests. Using mayonnaise might sound strange, but it’s the secret behind the moistness and depth of flavor you get here. Once you make this chocolate mayonnaise sheet cake recipe, you’ll understand why it stands out from your average chocolate cake.

Moist and Fudgy Texture: The mayonnaise keeps the cake incredibly tender without any greasy aftertaste.
Chocolatey Depth: The Dutch-processed cocoa powder mixed with coffee really makes the chocolate flavor sing.
Simple Prep: No fancy ingredients needed, and everything comes together quickly.
Versatile Sheet Cake: Perfect for potlucks, birthdays, or a casual weeknight treat because it serves a crowd and holds up well.

Ingredients & Why They Work

Before you dive in, let’s chat about the ingredients here—they’re simple, but every one plays an important role in making this cake sing. Plus, a quick shopping tip: using good-quality cocoa and fresh mayonnaise makes a noticeable difference in flavor and texture.

Flat lay of a small white ceramic bowl of all-purpose flour, a small white ceramic bowl of unsweetened Dutch processed cocoa powder, a small white ceramic bowl of light brown baking powder, a small white ceramic bowl of light brown baking soda, a small white ceramic bowl of coarse salt, a small white ceramic bowl of hot water with dissolved instant coffee powder, two large whole brown eggs with clean shells, a small white ceramic bowl of white granulated sugar, a small white ceramic bowl of packed brown sugar, a small white ceramic bowl of creamy mayonnaise, a small white ceramic bowl of amber vanilla extract, a small white ceramic bowl of finely chopped dark semisweet chocolate, a small white ceramic bowl of unsalted butter cubes, a small white ceramic bowl of powdered sugar, a small white ceramic bowl of heavy cream placed on a clean white marble surface, soft natural light, photo taken with an iPhone, professional food photography style, fresh ingredients, white ceramic bowls, no bottles, no duplicates, no utensils, no packaging --ar 2:3 --v 7 --p m7354615311229779997

All-Purpose Flour: The basic structure of your cake; makes it sturdy enough to hold all those luscious flavors.
Dutch-Processed Cocoa Powder: Offers a smooth, mellow chocolate flavor without bitterness—a must for a good chocolate mayonnaise sheet cake recipe.
Baking Powder & Baking Soda: Leavening agents that give the cake just the right amount of rise and lightness.
Salt: Enhances the chocolate’s richness and balances the sweetness beautifully.
Hot Water: Helps bloom the cocoa and instant coffee, boosting the chocolate flavor.
Instant Coffee Powder: A secret weapon that intensifies the chocolate without making the cake taste like coffee.
Eggs: Bind everything together and add moisture and richness.
White and Brown Sugar: Combination adds sweetness and subtle caramel undertones.
Mayonnaise: Sounds odd, but it’s all about fat and moisture—makes this cake incredibly tender.
Vanilla Extract: Adds a lovely layer of flavor that brings everything together.
Semisweet Chocolate (for frosting): Adds richness and melt-in-your-mouth decadence.
Unsalted Butter (for frosting): Creamy base for a luscious, spreadable frosting.
Powdered Sugar: Sweetens and smooths the frosting perfectly.
Heavy Cream: Lightens the frosting and gives it a silky finish.

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Note: You'll find the complete list of ingredients, along with their exact measurements, in the printable recipe card at the bottom of this post.

Make It Your Way

One of my favorite things about this chocolate mayonnaise sheet cake recipe is how open it is to your tweaks and personal touches. I often swap out ingredients or add extras depending on the occasion or my mood. You can easily tailor it to your taste without losing that classic moist texture.

Variation: I once added a handful of chocolate chips into the batter for extra melty pockets of chocolate—definitely a crowd-pleaser and perfect for a cozy night in.
Dietary Modification: For a dairy-free twist, you can substitute the butter in the frosting with coconut oil and use a nondairy mayo—just note the texture may be a bit different, but still delicious!
Seasonal Change: Around holidays, I sometimes sprinkle a pinch of cinnamon or cayenne into the batter for a warm, spicy kick.

Step-by-Step: How I Make Chocolate Mayonnaise Sheet Cake Recipe

A thick slice of dark chocolate cake with two layers is placed in the center of a round white plate with a gold rim. The bottom layer is a dense, moist dark brown cake with a rough texture, while the top layer is a smooth and creamy light brown chocolate frosting, spread unevenly with some soft peaks. A shiny gold fork rests diagonally on the lower left side of the plate. In the blurred background, two more slices of the same cake on white plates with gold rims sit on a white marbled surface, creating a cozy dessert setting. photo taken with an iphone --ar 2:3 --v 7

Step 1: Prep & Mix the Dry Ingredients

First things first, preheat your oven to 350°F (180°C) and grease your 9x13-inch pan with butter—this helps the cake release easily. Next, whisk together the flour, cocoa powder, baking powder, baking soda, and salt in a bowl until everything is evenly mixed. This ensures your cake rises uniformly with a consistent chocolate flavor. No lumps, no surprises.

Step 2: Brew the Coffee Mixture

Instant coffee might just seem like an odd baking detail, but it’s critical here. Dissolve the instant coffee powder in hot water, stirring well until it’s completely dissolved. This step really amplifies the chocolate notes without overpowering the cake. Set this aside while you prep the wet ingredients.

Step 3: Beat the Mayonnaise and Sugars

In a large bowl, beat the mayonnaise with the white and brown sugars until the mixture turns slightly pale and creamy. This usually takes about two minutes with an electric mixer. Don’t be alarmed by the texture—it may look a bit thick but that’s exactly what you want; it’s what makes this cake beautifully moist.

Step 4: Add the Eggs and Vanilla

Crack in the eggs one at a time, beating well after each addition. Make sure you scrape down the sides of your bowl periodically with a spatula to get everything well incorporated. Then pour in the vanilla extract and give it one last quick beat. This is where your batter starts looking dreamy.

Step 5: Combine Wet and Dry Ingredients Slowly

Time to marry the two mixtures! Add the dry ingredients in thirds, alternating with half of your coffee water each time. Beat gently until just combined after each addition. This delicate folding prevents overmixing—which can make cake tough—and keeps the batter silky smooth. Your batter should be thick but pourable, kind of like brownie batter.

Step 6: Bake and Cool

Pour the batter into your prepared pan and smooth out the top with a spatula. Bake for about 28 to 30 minutes. Use a toothpick inserted into the center to check doneness—it should come out with moist crumbs, not wet batter. A little sticky chocolate crumb is perfect! Let your cake cool completely before frosting, or you’ll end up with a melting mess.

Step 7: Make the Fudgy Frosting

While the cake cools, melt your chopped chocolate in the microwave in short bursts, stirring frequently so it doesn’t burn. Let it cool slightly while you beat the butter until creamy, then add powdered sugar gradually. Once smooth, beat in the cocoa powder, then add the cream and your cooled melted chocolate. Chill the frosting for about 10 minutes to thicken it—a perfect spreadable consistency.

Step 8: Frost and Enjoy!

Spread the luscious frosting evenly over your completely cooled cake. For a fun touch, use the back of a spoon or spatula to create swirls or peaks in the frosting. Slice, serve, and watch the smiles appear. This cake holds up well covered at room temperature for a day or refrigerated for longer storage.

Top Tip

Having made this chocolate mayonnaise sheet cake recipe more times than I can count, I’ve learned a few things that really take it from great to unforgettable.

Don't Skip the Coffee: Even a small amount of coffee intensifies the chocolate flavor without making the cake taste like coffee—trust me on this one.
Scrape the Bowl Well: Eggs and mayo like to stick around the edges. Scraping ensures an even batter and a consistent crumb.
Cool Completely Before Frosting: Frosting a warm cake causes it to melt and slide off—patience here makes a huge difference.
Chill Frosting Briefly: Letting the frosting set in the fridge before spreading helps it go on smoother and hold its shape.

How to Serve Chocolate Mayonnaise Sheet Cake Recipe

chocolate mayonnaise cake - Serving Suggestion

Garnishes

I usually keep it classic and simple—a light dusting of cocoa powder or a few fresh raspberries scattered on top. Sometimes I add a sprinkle of chopped toasted walnuts for crunch. These little touches add color and texture without stealing the spotlight from that rich chocolatey goodness.

Side Dishes

This cake pairs wonderfully with a dollop of lightly sweetened whipped cream or a scoop of vanilla bean ice cream. I’ve also served it alongside fresh strawberries or a bright berry compote to cut through the richness and balance the flavors.

Creative Ways to Present

For birthdays or celebrations, I’ve swirled in some caramel sauce over the frosting or added edible gold flakes for a little wow factor. You can even make mini versions in cupcake tins for individual servings that look so cute on a dessert tray.

Make Ahead and Storage

Storing Leftovers

I always keep leftover cake covered tightly with plastic wrap or stored in an airtight container. If unfrosted, the cake stays fresh at room temperature for up to 24 hours or refrigerated for up to a week. Once frosted, I store it in the fridge and let it come to room temperature before slicing to enjoy that perfect texture.

Freezing

Yes, this chocolate mayonnaise sheet cake freezes really well! I like to freeze it unfrosted, wrapped tightly in plastic and foil, then frost it fresh after thawing. If you freeze it frosted, let it thaw overnight in the fridge to avoid condensation sogginess and then bring it to room temp before serving.

Reheating

If you have leftover slices, you can microwave them for 15-20 seconds to soften the frosting slightly and enhance that warm, gooey cake feeling. It tastes almost like fresh-baked!

Frequently Asked Questions:

Is mayonnaise really necessary in the Chocolate Mayonnaise Sheet Cake Recipe?

Yes! Mayonnaise might seem unusual, but it adds fat and moisture, making the cake incredibly tender and rich without a greasy taste.

Can I use regular cocoa powder instead of Dutch-processed?

You can, but Dutch-processed cocoa powder provides a smoother, less bitter chocolate flavor, which really enhances this cake.

What’s the best way to store leftover frosted cake?

Store it in an airtight container or cover tightly in the refrigerator for up to 3 days. Before serving, let it come to room temperature to soften the frosting and enhance flavor.

Final Thoughts

This chocolate mayonnaise sheet cake recipe is one of those hidden gems that I love sharing because it feels like a special secret. The way the mayo makes the cake so moist, paired with that rich chocolate frosting, has become a tried-and-true favorite in my home—one that will surely become yours too. So go ahead, whip this up, and I promise you’ll be adding it to your rotation before long!