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 magical about a chocolate cake that’s moist, tender, and just a little unexpected. This Chocolate Mayonnaise Sheet Cake Recipe is exactly that kind of treat—rich chocolate flavor with a surprisingly silky texture thanks to mayonnaise. You’re going to be amazed how simple and delicious it is!

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 tried this Chocolate Mayonnaise Sheet Cake Recipe on a whim, and it quickly became my go-to for gatherings and weeknight indulgence. It’s rich yet light, incredibly moist, and that secret ingredient mayo? It keeps everything beautifully tender without any mayo flavor sneaking through—promise!

Unexpected Moisture: Mayonnaise adds a subtle richness and keeps the cake wonderfully soft and tender.
Deep Chocolate Flavor: With Dutch-processed cocoa and instant coffee powder, the chocolate taste is deeply layered and comforting.
Easy to Pull Together: No need to melt butter for the batter; mayo simplifies the mixing and saves time.
Perfect Sheet Cake Size: It’s great for parties or meal prepping—you can slice it up easily and serve lots of happy folks!

Ingredients & Why They Work

Each ingredient in this Chocolate Mayonnaise Sheet Cake Recipe has a specific role to create that luscious, soft cake you’ll crave. Knowing why they work together makes baking even more enjoyable and less intimidating.

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: Provides structure, but not too much, so the cake stays tender and soft.
Dutch-processed cocoa powder: Adds a rich, mellow chocolate flavor with deeper color and less acidity than natural cocoa.
Baking powder & baking soda: These leavening agents help the cake rise perfectly without being dense.
Salt: Balances the sweetness and enhances the chocolate flavors.
Hot water: Intensifies the cocoa flavor and helps dissolve the instant coffee powder for a subtle coffee kick.
Instant coffee or espresso powder: Doesn’t make the cake taste like coffee but boosts chocolate richness dramatically.
Eggs: Bind ingredients together and add moisture.
Sugar (white and brown): Brown sugar adds a hint of caramel complexity, while white sugar gives sweetness and structure.
Mayonnaise: This is the surprise that keeps your cake moist and fluffy without a mayo taste.
Vanilla extract: Adds warmth and lifts the chocolate flavor beautifully.
Semisweet or bittersweet chocolate: For the frosting, it provides a luscious, smooth decadence.
Unsalted butter: Creamy base for the frosting that helps it spread easily without being greasy.
Powdered sugar: Gives the frosting sweetness and silky texture.
Heavy cream: Adds richness and helps the frosting fold smoothly over the cake.

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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

I love how forgiving the Chocolate Mayonnaise Sheet Cake Recipe is, so feel free to tweak it to suit your vibe! I sometimes swap the instant coffee for espresso powder when I want a bolder note, and occasionally sprinkle a handful of chocolate chips in the batter for a melty surprise.

Dairy-Free Variation: I’ve swapped mayonnaise for a plant-based mayo and coconut cream for heavy cream, and it still turned out moist and lush, perfect for my vegan friends.
Nutty Twist: Adding chopped toasted walnuts or pecans on top of the frosting gives a lovely crunch that contrasts nicely with the softness.
Spiced Boost: Toss in a teaspoon of cinnamon or a pinch of cayenne pepper for a warm, unexpected flavor kick that I adore on chilly days.

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: Prepping the Pan and Mixing Dry Ingredients

First things first, I always preheat my oven to 350°F (180°C) and butter up my 9x13-inch baking pan. Greasing the pan with real butter—not spray—gives the edges a lovely brown crispness. Then, I whisk together all the dry ingredients: flour, cocoa, baking powder, baking soda, and salt, making sure they are well incorporated. This prevents any clumping and ensures even rising.

Step 2: Brewing the Coffee Mixture

While the oven heats, I dissolve the instant coffee or espresso powder into the hot water. This little trick is one of my favorite flavor boosters—it doesn’t make the cake taste like coffee, but it deepens the chocolate flavor beautifully. Set this aside to cool slightly while you move on.

Step 3: Mixing Mayonnaise and Sugars

I use an electric mixer to beat the mayonnaise with both white and brown sugars just until the mixture turns pale and creamy. This step is key because it dissolves some of the sugar early, helping the cake's crumb be extra tender later.

Step 4: Incorporating Eggs and Vanilla

Next, I add the eggs one at a time, beating well after each addition to fully combine. Scraping the bowl frequently here avoids any pockets of unmixed batter. Then in goes the vanilla extract for that warm, aromatic finish.

Step 5: Folding in Dry Ingredients and Coffee Mixture

This is where gentle mixing does wonders. I add the dry ingredients in thirds—mixing in half the coffee after the first third, the remaining coffee after the second, and the last third dry ingredients last. This back-and-forth avoids lumps and keeps the batter balanced—neither too thick nor runny.

Step 6: Baking to Perfection

Pour the batter evenly into your prepared pan and bake for about 28–30 minutes. I rely on the toothpick test here; you want it to come out with a few sticky crumbs, not a clean skewer. Let the cake cool completely—this is crucial so your frosting won’t melt.

Step 7: Creating the Luscious Frosting

For the frosting, I melt semisweet chocolate gently in the microwave in short bursts, stirring often to avoid burning. Then I beat softened butter with powdered sugar until fluffy, mix in cocoa powder, and finally add the heavy cream and cooled melted chocolate. After a quick chill in the fridge, it spreads like a dream.

Step 8: The Grand Assembly

Once your cake is fully cooled, spread the frosting evenly and create those signature swirls with a spatula or spoon back. It’s one of my favorite parts because the frosting is so velvety and inviting. Then, slice it up and watch it disappear!

Top Tip

From my experience, the secret to the best Chocolate Mayonnaise Sheet Cake Recipe really comes down to temperature and mixing technique. Here’s what I’ve learned the hard way that you’ll find invaluable:

Mayonnaise Quality: Use a good-quality mayonnaise with real ingredients—this affects the flavor and moisture.
Don’t Overmix: When adding dry ingredients, mix just until combined. Overmixing can make the cake tough.
Chocolate Cooling: Always cool the melted chocolate before adding it to the frosting to prevent it from seizing.
Room Temperature Ingredients: I always bring eggs and mayonnaise to room temperature for better mixing and texture.

How to Serve Chocolate Mayonnaise Sheet Cake Recipe

chocolate mayonnaise cake - Serving Suggestion

Garnishes

I like to keep the garnishes simple but effective—sprinkling a few chocolate shavings or a handful of toasted nuts on top adds a lovely texture. Sometimes, I dust a little powdered sugar for a pretty, understated look that makes it feel extra special.

Side Dishes

This cake pairs beautifully with a scoop of vanilla ice cream or a dollop of fresh whipped cream to balance the rich chocolate. On the savory side, a lightly brewed coffee or a robust red wine turns dessert time into a delightful mini celebration.

Creative Ways to Present

For birthdays or potlucks, I’ve served this sheet cake as mini squares on decorative platters, sometimes topped with edible flowers or fresh berries for a pop of color. You can also cut it into small cubes and serve with a fork for a cake bite station—always a hit!

Make Ahead and Storage

Storing Leftovers

Once baked but unfrosted, I cover the cake tightly with plastic wrap in the pan and keep it at room temperature for up to a day. Refrigerating the cake at this stage extends freshness for up to a week. After frosting, store it in the fridge, covered, for up to 3 days to keep the frosting firm.

Freezing

I’ve frozen unfrosted cake layers wrapped first in plastic wrap and then foil, and they defrost beautifully when left overnight in the fridge. Frosting is best fresh, but you can freeze slices with frosting by wrapping well and thawing slowly at room temperature.

Reheating

If you reheat a slice, I suggest taking it out of the fridge about 30 minutes before serving so the frosting softens without melting too much. For a quick warm-up, a few seconds in the microwave (covered with a damp paper towel) brings out the cake’s tender crumb.

Frequently Asked Questions:

Why is mayonnaise used in this Chocolate Mayonnaise Sheet Cake Recipe?

Mayonnaise adds moisture and fat which keeps the cake soft and tender without making it taste like mayo. It’s a clever substitute for oil or butter in the batter, creating a rich texture that lasts longer.

Can I make this cake gluten-free?

Yes! You can substitute the all-purpose flour with a gluten-free flour blend that is meant for baking. Make sure the blend contains xanthan gum or add it separately to help maintain structure.

How long can I store this cake after frosting it?

Once frosted, the cake keeps well in the refrigerator for up to 3 days. Be sure to bring it to room temperature before serving for the best texture and flavor.

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

You can, but the flavor and color may differ slightly. Dutch-processed cocoa is less acidic, giving a smoother chocolate taste and darker color. If you use natural cocoa powder, consider adding a bit more baking soda or an acid like buttermilk to balance the reaction.

Final Thoughts

This Chocolate Mayonnaise Sheet Cake Recipe has become one of those comforting desserts I reach for again and again. It feels like a little cheat because of the mayo, but honestly, it’s just smart baking. Give it a try—you’ll find the moist, flavorful crumb and easy prep a delightful surprise, perfect for sharing with friends or savoring solo.