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 irresistibly moist and richly chocolatey about this Chocolate Mayonnaise Sheet Cake Recipe. It’s a little secret weapon in the kitchen that makes the cake tender and full of flavor without a hint of mayo taste. Trust me, it’s magic you want in your baking repertoire.

The image shows a clear glass baking pan with a thick, dark brown chocolate cake inside. The cake has a smooth, shiny layer of light brown chocolate frosting spread evenly on top. Three square pieces are cut from the cake and are lying next to the cake inside the pan, showing the dense, moist texture of the dark cake beneath the frosting. The background has a white marbled texture. 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've made this Chocolate Mayonnaise Sheet Cake Recipe countless times, and every time it pulls me (and everyone else at the table!) right back in. The moist crumb, deep chocolate intensity, and easy one-pan prep make it a winner anytime – whether for casual family dinners or celebratory gatherings.

Super Moist Texture: The mayonnaise keeps the cake incredibly tender and rich without being greasy or heavy.
Deep Chocolate Flavor: Using both Dutch-processed cocoa and melted bittersweet chocolate amps up the chocolate deliciousness.
Simple Preparation: No complicated steps—just mix, bake, and spread frosting. Great for both beginner and seasoned bakers.
Flexible and Family-Friendly: It pleases kids and adults alike and can handle a variety of tasty customizations.

Ingredients & Why They Work

Each ingredient in this Chocolate Mayonnaise Sheet Cake Recipe plays a role in building that perfect structure and flavor. I always double-check for quality cocoa and fresh mayo for best results. Here's the lowdown on key players you’ll want to keep in mind when shopping:

Flat lay of a small pat of fresh unsalted butter, a neat pile of all-purpose flour, a mound of rich unsweetened Dutch processed cocoa powder, a small heap of light brown sugar, a small heap of white granulated sugar, two large whole brown eggs with clean shells, a modest scoop of creamy mayonnaise, a small white bowl filled with hot dark coffee dissolved with instant espresso powder, a small white bowl of pure vanilla extract, a small white bowl of finely chopped bittersweet chocolate, a small white bowl of heavy cream, and a small white bowl of powdered sugar, all arranged in perfect symmetry on a clean white ceramic surface, 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: Gives the cake its sturdy yet tender crumb; make sure to spoon and level for accuracy.
Dutch-processed cocoa powder: Adds a smooth, mellow chocolate flavor with a rich color—my favorite kind for chocolate cakes.
Baking powder & baking soda: Work together to ensure the cake rises nicely without being dense or spongy.
Instant coffee powder or espresso powder: Enhances and deepens the chocolate notes—it’s a baker’s little secret trick.
Mayonnaise: Yes, mayo! Its oil and eggs provide moisture while keeping the texture silky without that mayo taste.
Brown and white sugar: Combining both gives a more complex sweetness and a bit of caramel undertone.
Vanilla extract: Rounds out the flavors, giving warmth and aroma that makes the cake feel homey.
Semisweet or bittersweet chocolate: Used in the frosting for a decadent, melt-in-your-mouth finish.
Unsalted butter: Keeps control over saltiness and contributes to that luscious, creamy frosting texture.
Powdered sugar: Sweetens and lightens the frosting for the perfect spreadable consistency.
Heavy cream: Adds richness and smoothness to the frosting so it’s not too stiff and stays velvety.

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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 that this Chocolate Mayonnaise Sheet Cake Recipe is totally adaptable. Once you get the hang of the basics, try tweaking it to fit your taste or dietary needs—you’ll feel like a true kitchen pro!

Variation: I've swapped the instant coffee for a touch of cinnamon or orange zest sometimes—it gives a lovely twist without overshadowing the chocolate.
Dairy-Free: Use a vegan mayo and substitute almond or oat milk for cream in the frosting to keep it allergy-friendly without losing moisture.
Extra Decadent: Add chopped nuts like toasted pecans or swirl peanut butter into the batter for texture and flavor that wow guests.

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

The image shows a single square piece of dark chocolate cake with two layers on a white plate with a thin gold rim. The bottom layer is thick and dark brown with a moist, rich texture, while the top layer is a thick, smooth milk chocolate frosting with a slightly wavy surface. A golden fork rests on the plate next to the cake. In the background, two more pieces of cake on white plates with gold rims are slightly out of focus, all set on a white marbled textured surface. Photo taken with an iphone --ar 2:3 --v 7

Step 1: Prep Your Pan & Oven

Preheat your oven to 350°F (180°C). Then, lightly butter your 9x13-inch baking pan with softened butter. This ensures the cake won't stick and helps it come out clean without tearing. I’ve learned the hard way that a proper greased pan is key here!

Step 2: Mix Dry Ingredients Thoroughly

In a medium bowl, whisk together the flour, Dutch-processed cocoa, baking powder, baking soda, and salt. Make sure the cocoa and leaveners are well combined for even rising and flawless chocolate flavor throughout. This is your foundation, so don’t rush.

Step 3: Dissolve Coffee in Hot Water

Stir the instant coffee powder into the hot water until fully dissolved. This step is a subtle magic trick—it’s not about making it taste like coffee, but elevating the chocolate’s richness. Let this cool slightly while you move on.

Step 4: Beat Mayonnaise and Sugars

Using an electric mixer, beat the mayonnaise with both sugars until the mixture lightens and becomes creamy. This usually takes about two minutes. Scrape the bowl’s sides to keep everything homogenous—it really helps with smooth batter later.

Step 5: Add Eggs and Vanilla

Add the eggs one at a time, beating well after each addition. Remember to scrape down the bowl again to prevent any clumps. Pour in the vanilla extract and beat just to combine—it keeps the batter balanced and flavorful.

Step 6: Alternate Adding Dry Ingredients and Coffee

Add your dry ingredients in three parts, alternating with the hot coffee in two parts. Start with one-third of the dry mix plus half the coffee, beat gently until combined, then repeat. Finish by stirring in the last third of dry ingredients. The batter should feel thick but still pourable—a perfect balance.

Step 7: Bake and Cool

Pour the batter evenly into your prepared pan and bake for 28-30 minutes. Use a toothpick to check doneness—it should come out with moist crumbs, not wet batter. When done, let the cake cool completely. Patience here pays off when spreading the frosting later.

Step 8: Make the Decadent Frosting

Microwave the chopped bittersweet chocolate in 20-second bursts, stirring in between until smooth. Let cool slightly to avoid melting the butter later.

Beat softened butter until fluffy, then gradually add powdered sugar on low speed, increasing to high to get a light, creamy base. Mix in the cocoa powder, scraping sides for smoothness.

Finally, add the heavy cream and the cooled melted chocolate, beating until luscious and glossy. Chill in the fridge for about 10 minutes so it firms enough to spread without sliding off.

Step 9: Frost and Serve

Spread the frosting evenly over the fully cooled cake. Use a spatula or back of a spoon to create swirls—I find this adds a fun rustic charm. Slice, serve, and watch everyone smile with that first bite.

Top Tip

From my many adventures making this cake, a few tips have really made a difference in a perfectly moist, smooth finish every time.

Use Dutch-processed Cocoa: It’s softer, less acidic, and blends beautifully, giving that deep chocolate glow and flavor I love.
Don’t Skip the Coffee: It intensifies chocolate without making it taste like coffee—every time I forget it, the cake feels flat.
Cool the Cake Completely: Frosting a warm cake leads to melted, runny icing—cooling avoids this disaster and keeps your swirls neat.
Slightly Cool Melted Chocolate Before Adding: Hot chocolate can melt your frosting base, causing it to lose that creamy structure.

How to Serve Chocolate Mayonnaise Sheet Cake Recipe

chocolate mayonnaise cake - Serving Suggestion

Garnishes

I usually keep it simple—just a light dusting of powdered sugar or a few fresh raspberries on top for a beautiful, fresh pop. For holidays, a sprinkle of chopped toasted pecans or coconut flakes adds texture and flair that guests love.

Side Dishes

This cake pairs wonderfully with a scoop of vanilla ice cream or a dollop of lightly whipped cream on the side. Fresh berries or a bright citrus salad balance the richness nicely and add a fresh contrast.

Creative Ways to Present

For birthdays or gatherings, try cutting the sheet cake into neat squares and stacking a few pieces on a pretty plate to create a small “tower.” Drizzle with chocolate sauce or caramel for extra charm. I’ve also served it in mini sheet pans for portion control at potlucks.

Make Ahead and Storage

Storing Leftovers

Once baked, leave the cake covered in its baking pan with plastic wrap at room temperature for up to one day or refrigerate for up to a week. After frosting, I store it in the fridge tightly covered, and it stays delicious for about three days. Just remember to bring it back to room temp before serving—the frosting softens perfectly.

Freezing

I’ve frozen unfrosted cake layers wrapped in plastic wrap and foil, and they thaw beautifully overnight in the fridge. Frost once thawed for best results. You can also freeze the fully frosted cake in an airtight container—just let it thaw slowly on the counter before enjoying.

Reheating

To revive leftover cake, remove from the fridge and let it warm to room temperature for about 30 minutes before slicing. If you prefer a warmer slice, microwave a single piece for 10-15 seconds to melt that frosting just a touch, bringing out the gooey richness.

Frequently Asked Questions:

Does the mayonnaise make the cake taste like mayo?

Not at all! Mayonnaise acts as a secret ingredient that adds moisture and richness, but its flavor disappears during baking, leaving only a tender crumb and wonderfully moist texture.

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

You can use regular cocoa powder, but Dutch-processed cocoa has a smoother, less acidic flavor that enhances the cake’s chocolate notes. If substituting, consider adding a pinch of baking soda to balance acidity.

Why do you add coffee to the batter?

The instant coffee powder intensifies the chocolate flavor without imparting a coffee taste. It’s a common baking trick to deepen chocolate richness and make it more vibrant.

How long does this cake stay fresh?

Baked but unfrosted, the cake stays fresh covered at room temperature for one day or refrigerated for up to seven days. Once frosted, it’s best enjoyed within three days if kept refrigerated. Always let it come to room temp before serving.

Final Thoughts

This Chocolate Mayonnaise Sheet Cake Recipe has become my go-to whenever I want a chocolate dessert that’s soft, indulgent, and straightforward. It's my little kitchen secret that never fails to impress friends and family. I hope you’ll love making and sharing it as much as I have—it’s one of those recipes that feels like a warm, sweet hug on a plate.