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 wonderfully surprising about this dessert — rich, moist, and utterly decadent, the Chocolate Mayonnaise Sheet Cake Recipe is a total game changer in the world of chocolate cakes. It’s super simple but delivers such a tender crumb and deep chocolate flavor that you'll keep coming back for more.

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

The charm of this cake lies not only in its luscious flavor but also in its unexpected ingredient — mayonnaise. Trust me, the mayo isn’t there to make it weird; it actually makes this cake incredibly moist and fluffy, with a texture that’s hard to beat. I’ve made this recipe many times when I wanted an impressive dessert without fuss.

Unbelievably moist: The mayonnaise keeps the cake tender and moist without that greasy feeling.
Easy to make: Simple ingredients and straightforward steps means you won’t feel overwhelmed.
Rich chocolate flavor: The combination of cocoa and coffee powder really enhances the depth of chocolate in every bite.
Perfect for any occasion: From casual family dinners to potlucks, this sheet cake is always a crowd-pleaser.

Ingredients & Why They Work

Each ingredient in this Chocolate Mayonnaise Sheet Cake Recipe plays its specific part to create that perfect balance of texture and flavor. The rich cocoa and instant coffee deepen the chocolate notes, while the mayonnaise surprisingly acts as both a fat and an emulsifier, making the cake moist without oil or butter in the batter.

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: Provides the structure; sifted well for a tender crumb.
Unsweetened Dutch processed cocoa powder: Brings a rich chocolate flavor and a beautiful dark color.
Baking powder and baking soda: These leavening agents create lift and lightness.
Salt: Balances the sweetness and enhances overall flavor.
Instant coffee powder: Intensifies the chocolate flavor without tasting like coffee.
Eggs: Add richness and help bind the cake together.
Sugar (white and brown): The combination adds sweetness and a slight molasses depth.
Mayonnaise: The secret to moisture and tenderness, thanks to its oil and egg content.
Vanilla extract: Rounds out all the flavors beautifully.
Semisweet or bittersweet chocolate (for frosting): Gives a luscious, glossy finish and added chocolate punch.
Unsalted butter (for frosting): Makes the frosting creamy and smooth.
Powdered sugar: Sweetens and thickens the frosting without grit.
Heavy cream: Adds silkiness and makes the frosting spreadable.

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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 playing around with this Chocolate Mayonnaise Sheet Cake Recipe to suit whatever mood I’m in or what I have in the pantry. It’s so forgiving and versatile, I encourage you to add your own twists for a personal touch.

Variation: I sometimes swap half the cocoa powder for dark cocoa to get an even deeper, almost bittersweet flavor — it’s fantastic if you enjoy intense chocolate.
Dietary modification: For a dairy-free version, try using a vegan mayo and coconut cream in the frosting; it works surprisingly well!
Seasonal change: Adding a teaspoon of orange zest into the batter really brightens the chocolate and pairs beautifully with the creamy frosting.

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 and Dry Ingredients

Start by preheating your oven to 350°F (180°C). Butter your 9x13-inch baking pan gently—no need for anything fancy, just a little grease to keep the cake from sticking. Then, in a medium bowl, whisk together your flour, cocoa, baking powder, baking soda, and salt. This ensures everything's evenly distributed and avoids clumping — trust me, a smooth batter makes all the difference!

Step 2: Mix the Coffee and Beat the Sugars with Mayonnaise

Next, dissolve your instant coffee powder into hot water — you’ll be surprised how this tiny addition amplifies the chocolate. In a large bowl, beat the mayonnaise with both the white and brown sugars until it’s nice and creamy. The mixture should look slightly pale, and you’ll want to scrape down the sides often so everything blends perfectly.

Step 3: Add Eggs and Vanilla

Now add the eggs—one at a time—beating well after each addition. This gives the batter structure and richness. Follow with the vanilla extract for warmth and flavor complexity. Scrape down those bowl sides often; leaving unincorporated bits never helps!

Step 4: Combine Dry Ingredients and Coffee with Wet Mixture

Divide your dry mix into thirds. Add the first third of the dry ingredients along with half of the coffee mixture to the wet ingredients and beat gently but thoroughly. Repeat with the second third and remaining coffee, beating well. Finally, fold in the last third of flour mixture. Your batter should be smooth — not too stiff, not runny. That's texture perfection right there.

Step 5: Bake the Cake

Pour your batter into the greased pan and smooth the top with a spatula. Bake for 28 to 30 minutes. To check doneness, insert a toothpick in the center; it should come out with moist crumbs, not wet batter. Let the cake cool completely before you even think about frosting — I’ve learned patience really pays off here.

Step 6: Make the Creamy Chocolate Frosting

While the cake cools, melt your chocolate in 20-second bursts in the microwave, stirring each time until smooth. Set it aside to cool slightly — this step helps avoid scrambling your frosting. In a large bowl, beat butter until soft and fluffy, then gradually add powdered sugar. Up the mixer speed as it combines, beating for a couple of minutes to get that light texture.

Add cocoa powder and mix well, scraping the bowl sides. Finally, pour in the heavy cream and the melted chocolate, and beat until everything is luscious and creamy. Pop it in the fridge for 10 minutes to firm up a bit before frosting.

Step 7: Frost and Enjoy

Use a spatula or the back of a spoon to spread your frosting evenly over the cooled cake; I love swirling it a bit for a homemade, rustic look. Slice, serve, and get ready for those delicious compliments!

Top Tip

Over the years, I've found some little tricks that really make this recipe shine and keep it easy to pull off without stress.

Don’t Skip the Coffee: Even if you’re not a coffee drinker, the instant coffee powder enriches the chocolate flavor without noticeable coffee taste, giving the cake a deeper, more complex flavor.
Mayonnaise Quality Matters: Use a good-quality mayo for best results—it's the oil and eggs in there that make the cake tender, so nothing low-fat or weirdly flavored.
Cool Completely Before Frosting: This can’t be overstated; frosting warm cake makes it melt and get messy, but frosting cold cake keeps it neat and beautiful.
Beat the Frosting Well: Take your time with the frosting—it should be fluffy and smooth; this airiness adds to that dreamy texture when you bite in.

How to Serve Chocolate Mayonnaise Sheet Cake Recipe

Chocolate Mayonnaise Cake - Serving Suggestion

Garnishes

I often sprinkle a handful of flaky sea salt over the frosting to contrast the sweetness and highlight the chocolate. Fresh raspberries or a few mint leaves can brighten it up too if you want to fancy it up a bit.

Side Dishes

Pairing this cake with a scoop of vanilla bean ice cream or a dollop of lightly whipped cream has never disappointed. A strong cup of coffee or cold milk also complements the rich chocolate—trust me, it’s a classic combo you can’t go wrong with.

Creative Ways to Present

For birthdays, I like to pipe rosettes of frosting along the edges and scatter chocolate shavings or sprinkles on top. Turning it into mini portions by cutting into bite-sized squares on a pretty platter makes it perfect for parties.

Make Ahead and Storage

Storing Leftovers

I keep the unfrosted cake in the baking pan covered tightly with plastic wrap at room temperature for up to 24 hours. If I need to keep it longer, the fridge works for about a week. Once frosted, I store leftovers in an airtight container in the fridge for a few days.

Freezing

If you want to save some for later, freeze the unfrosted cake wrapped well in plastic and foil. When ready, thaw overnight in the fridge and frost the next day. The texture holds up beautifully if you do it this way!

Reheating

To enjoy leftover slices, I recommend bringing them to room temperature before eating. If you want it warm, pop a piece in the microwave for 10-15 seconds, but I usually avoid heating the frosting to keep it from melting too much.

Frequently Asked Questions:

Can I substitute the mayonnaise with something else?

Mayonnaise is key to the moisture and texture in this cake because it contains both oil and eggs, which keep it tender. You could try sour cream or Greek yogurt as substitutes, but the texture may differ slightly and possibly be less rich.

Is the coffee flavor noticeable in the cake?

The instant coffee powder is there to enhance the chocolate’s depth, not to make the cake taste like coffee. Most people don’t even notice it’s there, but they comment on how rich the chocolate flavor is.

Can I make this cake gluten-free?

Yes! You can substitute the all-purpose flour with a one-to-one gluten-free baking flour blend. Just make sure it includes xanthan gum or another binder to keep the cake’s structure intact.

How long does this cake last?

At room temperature with frosting, the cake is best enjoyed within 1-2 days. If refrigerated, it will keep well for up to 3 days. Unfrosted and wrapped tightly, it can last a week in the fridge or up to 3 months in the freezer.

Final Thoughts

This Chocolate Mayonnaise Sheet Cake Recipe will surprise you with its ease and the depth of that chocolatey goodness. Every time I bring this cake to a gathering, it disappears fast, and I love how simple it is to make look impressive. Give this one a try—you might just find your new go-to chocolate cake that’s as comforting as it is delicious.