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 unexpectedly delightful about this Chocolate Mayonnaise Sheet Cake Recipe. It’s rich, moist, and has this incredible, almost fudgy texture that makes every bite feel like a special treat. Trust me, you’ll want to keep this recipe handy for any occasion.

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

I first stumbled on this cake at a friend’s potluck, and honestly, I was skeptical about mayonnaise in a dessert. But once I took a bite, I was sold! It’s wonderfully moist and rich without feeling heavy or greasy. It’s one of those rare cakes that balances indulgence and comfort perfectly.

Super Moist Texture: Thanks to mayonnaise, the cake stays delectably soft and doesn’t dry out even a day later.
Easy to Make: No fancy equipment or complicated techniques – just simple steps and straightforward ingredients.
Rich Chocolate Flavor: Cocoa powder and melted chocolate in the frosting bring deep, satisfying chocolate notes that everyone loves.
Great for Gatherings: The sheet cake size means plenty to share – perfect for parties, family dinners, or quick celebrations.

Ingredients & Why They Work

Each ingredient here plays a crucial role in making the Chocolate Mayonnaise Sheet Cake Recipe a standout. The combination of cocoa powder, instant coffee, and mayonnaise delivers a cake that's super moist and has intense chocolate depth. Here are some quick tips about why these ingredients matter and how to pick the best ones.

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 base of your cake, it provides structure without being too dense. Make sure to spoon and level when measuring to avoid a dry crumb.
Dutch processed cocoa powder: Using Dutch processed cocoa (not natural) gives a smoother, deeper chocolate flavor and a darker color.
Baking powder and baking soda: These leavening agents work together to give the cake the right lift and tenderness.
Salt: Just a pinch enhances all the chocolate flavors and balances the sweetness.
Instant coffee powder or espresso powder: Coffee intensifies the chocolate taste without making the cake taste like coffee.
Mayonnaise: The secret hero here! It keeps the cake moist and tender thanks to its oil and eggs content, but you won’t taste mayo at all.
Sugars (white and brown): Using a mix adds balance – white sugar sweetens, brown sugar gives a subtle caramel note and moistness.
Eggs: They bind ingredients and contribute richness and structure.
Vanilla extract: Enhances all the flavors and rounds out the chocolate.
Butter (for greasing): Prevents sticking and adds a subtle buttery hint around the edges.
For the frosting – semisweet or bittersweet chocolate: Choose quality chocolate you love to eat on its own for best results.
Unsalted butter: Creamy base for the frosting, adds richness without being salty.
Powdered sugar: Sweetens and smooths the frosting to a creamy texture.
Heavy cream: Adds smoothness and helps achieve a luscious consistency.

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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

This Chocolate Mayonnaise Sheet Cake Recipe is a wonderful starting point, and I often switch it up depending on the occasion. Feel free to tweak it to match your mood or pantry!

Variation: I sometimes add a handful of chocolate chips or chopped nuts into the batter for extra texture—it's a family favorite twist!
Dietary tweak: For a dairy-free version, swap butter with plant-based margarine and use a dairy-free mayo; it still turns out great.
Seasonal change: Try adding a teaspoon of cinnamon or a splash of orange extract to the batter for warm, cozy notes in fall and winter.

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 your pan and ingredients

First things first, preheat your oven to 350°F (180°C) and lightly butter a 9x13-inch sheet pan. I find that a generous buttering helps the cake release beautifully without sticking. Next, sift together the dry ingredients — the flour, cocoa powder, baking powder, baking soda, and salt — to ensure everything is evenly mixed.

Step 2: Dissolve the coffee for richness

In a small jug or bowl, mix your hot water with instant coffee powder until fully dissolved. Don't skip this step—it sounds small, but it really elevates the chocolate’s depth, making the cake irresistibly flavorful.

Step 3: Beat the mayonnaise and sugars

Using an electric mixer, beat the mayonnaise together with white and brown sugar until the mixture turns pale and creamy—this usually takes around 2-3 minutes. This step might feel a little odd since mayo isn't typical in cakes, but it’s key to that soft texture. Remember to scrape down the sides so nothing gets left behind.

Step 4: Add the eggs and vanilla

Add your eggs one at a time, mixing well after each addition. This helps build a smooth batter and ensures the eggs are fully incorporated. Then pour in the vanilla extract and give it all another good whisk.

Step 5: Combine the dry ingredients and coffee in batches

Now comes the fun part! Add the dry ingredients in thirds to the wet mixture, alternating with the coffee liquid. Start by adding the first third of the dry mix and half of the coffee, beat until combined. Repeat with the second third of dry ingredients and the remaining coffee. Finally, add the last third and mix until smooth. The batter should be balanced — not too thick, not too runny.

Step 6: Bake to perfection

Pour the batter into your prepared pan and pop it in the oven for 28 to 30 minutes. I like to start checking at 28 minutes with a toothpick – it should come out with moist crumbs but no wet batter. Let the cake cool completely before frosting to avoid a melty mess.

Step 7: Make the luscious frosting

Melt the chopped chocolate in short bursts in the microwave, stirring frequently to avoid burning. Then beat room temperature butter until fluffy, gradually add powdered sugar, then cocoa powder. Fold in the heavy cream and cooled melted chocolate, beating well to combine. Chill the frosting for about 10 minutes until it’s spreadable.

Step 8: Frost and serve

Spread the frosting evenly over the cooled cake using a spatula or the back of a spoon. I love making little swirls for that rustic, homemade look. Slice, serve, and get ready for the compliments!

Top Tip

After my first few tries, I learned some key tips that really make a difference. These little tricks saved me from common pitfalls and made the Chocolate Mayonnaise Sheet Cake Recipe a reliable favorite.

Don't Skip the Coffee: Even if you don’t want a coffee flavor, adding instant coffee sharpens and deepens the chocolate taste remarkably.
Beat the Mayo and Sugars Well: This step aerates the mixture, resulting in a lighter crumb than you'd expect from mayo-based cake.
Cool the Chocolate Before Mixing: Avoid adding warm melted chocolate straight into the frosting — it can melt the butter and ruin texture.
Test Your Cake Early: Start testing with a toothpick at 28 minutes to keep the crumb moist and fudgy, not dry and overbaked.

How to Serve Chocolate Mayonnaise Sheet Cake Recipe

Chocolate Mayonnaise Cake - Serving Suggestion

Garnishes

I usually stick to a simple garnish — a light dusting of cocoa powder or a few fresh raspberries on top to add a pop of color and tartness. Sometimes I sprinkle shaved chocolate curls for an elegant touch. These little extras make it feel festive without overpowering the rich chocolate flavor.

Side Dishes

This sheet cake pairs beautifully with a scoop of vanilla ice cream or a dollop of whipped cream—perfect for balancing the rich chocolate. For grown-up gatherings, a glass of cold milk or a cup of fresh-brewed coffee complements it wonderfully, too.

Creative Ways to Present

For birthdays or celebrations, I love decorating with colorful sprinkles or edible flowers. You can also cut the cake into squares, place each piece in cupcake liners, and serve them as individual treats—great for casual parties or picnics. It always gets a wow!

Make Ahead and Storage

Storing Leftovers

Once baked, I keep the cake in the pan and cover it tightly with plastic wrap. It stores well at room temperature for a day, or in the fridge up to a week. If unfrosted, the cake holds its moisture very well, and if frosted, it’s best eaten within three days.

Freezing

I’ve frozen this cake both before and after frosting. To freeze, wrap tightly with plastic wrap and a layer of foil. When you’re ready to enjoy, thaw overnight in the fridge. The texture remains just as good, making it perfect to prepare in advance for busy days or events.

Reheating

If you want a warm slice, I pop individual pieces in the microwave for 10-15 seconds—but I always remove the frosting first since it doesn’t warm well. Alternatively, enjoy the cake cooled or at room temperature for the best texture and flavor balance.

Frequently Asked Questions:

Can I substitute mayonnaise with something else?

Mayonnaise is the key to the cake’s moist texture, but you can try substituting it with an equal amount of sour cream or Greek yogurt for similar results. Keep in mind the texture might be slightly different.

Why does this recipe use instant coffee in a chocolate cake?

The instant coffee amplifies the chocolate flavor without making the cake taste like coffee. It adds depth and richness, which makes the chocolate taste more intense and complex.

Can I make this cake gluten-free?

To make this cake gluten-free, substitute the all-purpose flour with a gluten-free flour blend that’s designed for baking. Make sure the blend contains xanthan gum for structure, and keep in mind the texture may vary slightly.

How long will the frosted cake stay fresh?

The frosted cake is best eaten within 3 days when stored in the refrigerator. Before serving, let it come to room temperature to soften the frosting for the best texture and flavor.

Final Thoughts

Every time I make this Chocolate Mayonnaise Sheet Cake Recipe, it feels like sharing a little secret with friends and family — it’s so simple, yet the results are truly impressive. If you haven’t tried a mayo-based cake before, this recipe will change your mind and your baking game. It’s a delicious, reliable go-to that I hope becomes a favorite in your kitchen, just like it is in mine.