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

Prepare to fall for the ultimate crowd-pleaser: Chocolate Mayonnaise Sheet Cake. This glorious, one-pan chocolate cake bakes up irresistibly tender thanks to a secret ingredient that was all the rage in the mid-century—mayonnaise! With deep chocolate flavor, a plush crumb, and a glossy, swoopy frosting, it’s the type of decadent dessert you can serve for a birthday, potluck, or just because you want a square of old-school comfort. If you’ve never tried mayo in cake before, you’re in for a delicious surprise.

Chocolate Mayonnaise Sheet Cake Recipe - Recipe Image

Ingredients You’ll Need

What I love about this recipe is how simple, everyday ingredients become something surprisingly special. Each component works together to create rich flavor and that legendary moistness—for a Chocolate Mayonnaise Sheet Cake you’ll dream about long after the last crumb is gone!

Butter, for greasing: Prepping your pan with butter is the first smart step for easy cake release and deeper flavor.
All-purpose flour (2 cups): Provides structure while keeping the crumb tender.
Unsweetened Dutch processed cocoa powder (1 cup): Gives the cake its intense, smooth chocolate character.
Baking powder (1 1/2 tsp): Helps the cake rise beautifully.
Baking soda (1 1/2 tsp): Works with the mayo and cocoa for the perfect, pillowy texture.
Salt (1/4 tsp): Enhances everything; never skip it with chocolate!
Hot water (3/4 cup): Unlocks cocoa’s deep flavor for a richer cake base.
Instant coffee or espresso powder (2 tbsp): Intensifies the chocolate notes—your secret flavor enhancer.
Large eggs (2): For structure, richness, and that good old-fashioned cake springiness.
Sugar (1 cup): Sweetens and softens the crumb.
Brown sugar (1/2 cup): Adds subtle caramel notes and extra moisture.
Mayonnaise (1 cup): The star! Its oil and eggs make the cake uniquely plush and moist.
Vanilla extract (1 tbsp): Rounds out and boosts sweet, aromatic flavors.
Finely chopped semisweet or bittersweet chocolate, for frosting (1/2 cup): Melts into the silkiest frosting topping.
Unsalted butter, for frosting (1/2 cup): Guarantees a creamy, airy spread.
Unsweetened Dutch processed cocoa powder, for frosting (2 tbsp): More cocoa means bolder chocolate flavor in every bite.
Powdered sugar, for frosting (1 cup): Gives the frosting cloud-like sweetness and smooth texture.
Heavy cream, for frosting (1/2 cup): Brings the frosting to luscious, spreadable life.

How to Make Chocolate Mayonnaise Sheet Cake

Step 1: Prep the Pan and Preheat the Oven

Start by turning your oven to 350°F (180°C) so it’s piping hot when you’re ready. Grab your trusty 9×13-inch sheet pan and grease it with a swipe of butter—this ensures an easy release and a hint of buttery crispness on every edge.

Step 2: Combine the Dry Ingredients

In a medium bowl, whisk together the flour, Dutch processed cocoa, baking powder, baking soda, and salt. This step might seem basic, but even mixing guarantees every bite of this Chocolate Mayonnaise Sheet Cake is evenly chocolatey and perfectly fluffy.

Step 3: Mix Hot Coffee with Water

Measure out the hot water, then stir in your instant coffee or espresso powder until it dissolves completely. This little trick wakes up the cocoa’s full potential with a whisper of coffee flavor—don’t skip it!

Step 4: Cream the Mayonnaise and Sugars

Combine the mayonnaise, white sugar, and brown sugar in a large mixing bowl. Use an electric beater and mix until the blend turns creamy and a little pale—this is the magic that makes your cake so airy and moist.

Step 5: Add Eggs and Vanilla

Crack in the eggs, one at a time, beating well after each addition. Pause to scrape the bowl, add the vanilla extract, and give everything another mix. You’re building rich flavor and structure for your cake.

Step 6: Fold Everything Together

Begin alternating the dry mix and the coffee mixture into your creamed mayo base. Add the first third of dry ingredients along with half the coffee, mix, then repeat. Finish with the last third of dries and beat until your batter is glossy and thick, but not too stiff or thin.

Step 7: Bake Your Cake

Pour the beautiful batter into your prepared pan and smooth the top. Slide it into the oven and bake for 28 to 30 minutes, or until a toothpick comes out with only moist crumbs. Let your Chocolate Mayonnaise Sheet Cake cool completely in the pan before you even think about frosting—it’s worth the wait!

Step 8: Make the Silky Chocolate Frosting

While your cake cools, melt the chopped chocolate in the microwave (try 20-second bursts) and let it cool slightly. In a separate bowl, beat the butter until creamy, then mix in the powdered sugar gradually. Add cocoa powder and beat again until fluffy. Stir in the cooled chocolate and heavy cream, then chill for 10 minutes to firm it up—hello, glossy decadence.

Step 9: Frost and Serve

Once your cake is cool, spread the frosting evenly over the top, swirling to your heart’s content. Cut generous squares and admire the dreamy, luscious layers before diving in!

How to Serve Chocolate Mayonnaise Sheet Cake

Garnishes

Finish your Chocolate Mayonnaise Sheet Cake with a flourish: try a light dusting of powdered sugar, a handful of chocolate curls, or even a sprinkle of flaky sea salt for a grown-up twist. A few fresh berries on top make the presentation pop and add a welcome zing.

Side Dishes

Pair your cake with a scoop of vanilla ice cream, a dollop of whipped cream, or even fresh cherries for a classic combo. If you want to keep things lighter, serve with a bowl of fresh raspberries or strawberries—their tartness is the perfect foil for all that chocolate richness.

Creative Ways to Present

This sheet cake is a canvas for your creativity! Try cutting it into fun shapes for a birthday party, layering squares with frosting and berries for an elegant trifle, or serving tiny cubes as bite-sized treats for a dessert buffet. Chocolate Mayonnaise Sheet Cake is endlessly adaptable for any gathering.

Make Ahead and Storage

Storing Leftovers

Once cooled and frosted, you can keep your Chocolate Mayonnaise Sheet Cake right in the pan, covered tightly with plastic wrap. It will stay fresh at room temperature for a day, or in the refrigerator for up to 3 days. Just remember to let it warm up a bit before diving in, so the frosting is smooth and creamy again.

Freezing

Great news for planners—this cake freezes beautifully! For the best texture, freeze individual unfrosted squares wrapped in plastic. For frosted cake, place the pan in the freezer (uncovered) until the frosting is firm, then wrap well and freeze for up to 2 months. Thaw slices overnight in the fridge before serving.

Reheating

If you love a slightly warm slice, microwave individual portions for just 10 to 15 seconds to revive that just-baked coziness. Be gentle—overheating can dry out your Chocolate Mayonnaise Sheet Cake, so keep it quick!

FAQs

Can I use regular cocoa powder instead of Dutch processed?

You can swap in natural cocoa powder if that’s what you have, but Dutch processed will give your cake a smoother, richer chocolate flavor and deeper color. The difference is subtle, but for classic Chocolate Mayonnaise Sheet Cake, Dutch processed really shines.

Does the cake actually taste like mayonnaise?

Not at all! The mayonnaise melts into the cake, giving it moisture and tenderness with zero mayo flavor. Think of it as a sneaky hack for incredible texture—no one will ever guess your secret.

Can I make this cake gluten-free?

Absolutely. Substitute your favorite 1:1 gluten-free baking flour blend for the all-purpose flour. The result will still be soft and rich, so everyone can enjoy a slice of Chocolate Mayonnaise Sheet Cake.

Is there a way to make the frosting ahead of time?

Yes! You can prepare the frosting up to three days in advance. Just store it in an airtight container in the fridge, then let it soften and re-whip briefly before spreading on your cooled cake.

What if I don’t have espresso powder?

If you don’t have instant coffee or espresso powder, no worries—the cake will still be delicious. The coffee merely deepens the chocolate flavor, so you can leave it out or substitute with decaf coffee powder if preferred.

Final Thoughts

If you’ve been searching for the ultimate easy dessert, do yourself a favor and make this Chocolate Mayonnaise Sheet Cake. It’s rich, reliable, and ridiculously moist, with a nostalgia factor that makes it perfect for any occasion. Give it a try, and you might just find it becomes your new go-to cake recipe!