This Double Chocolate Mayonnaise Cake is a deeply chocolatey, exceptionally moist 13 x 9-inch dessert made with cocoa, semisweet chocolate chips, and full-fat mayonnaise. It takes just 15 minutes to prepare and bakes at 350°F (175°C) for 30–35 minutes, making it a practical homemade cake for birthdays, potlucks, holidays, or an ordinary chocolate craving.
The mayonnaise does not make the cake taste savory. Instead, it contributes oil and egg, helping create a soft, tender crumb while the cocoa and chocolate chips provide rich, layered chocolate flavor. Finished with a smooth cocoa frosting, every bite is fudgy, creamy, and decadent without being difficult to prepare.
Jump to RecipeWhy You’ll Love This Recipe
There is something wonderfully nostalgic about a simple sheet cake, especially one that fills the kitchen with the aroma of cocoa and warm chocolate. This version has the familiar ease of a pan cake but delivers a remarkably plush crumb that stays tender after cooling.
The chocolate flavor comes from two sources: unsweetened baking cocoa in the batter and a full cup of semisweet chocolate chips folded in before baking. The chips create little pockets of chocolate throughout the cake, while the cocoa gives the crumb its dark, classic chocolate character.
Mayonnaise is the surprising ingredient that makes this recipe special. Because it contains oil and egg, it supplies much of the fat and emulsifying power that butter and additional eggs often provide in other cakes. The result is moist and soft without requiring a complicated mixing method.
If you enjoy generous chocolate desserts, you may also like this rich chocolate cake idea for another celebration-worthy bake.
Ingredients You’ll Need
The ingredient list is short, familiar, and easy to keep on hand. Measure the flour and cocoa carefully for the most reliable texture, and use full-fat mayonnaise rather than a reduced-fat variety.
- All-purpose flour: Gives the cake enough structure while keeping the crumb tender.
- Granulated sugar: Sweetens the cocoa and helps the cake retain moisture.
- Unsweetened baking cocoa: Provides the deep chocolate base in both the cake and frosting.
- Baking soda and salt: Help the cake rise and balance the sweetness.
- Mayonnaise: Adds richness, moisture, oil, and egg-based emulsification.
- Water: Loosens the batter and allows the cocoa to blend smoothly.
- Eggs and vanilla: Add structure, flavor, and a rounded finish.
- Semisweet chocolate chips: Create extra chocolate flavor and a pleasantly soft bite.
For the frosting, you will need softened unsalted butter, cocoa, milk, confectioners’ sugar, and vanilla. The frosting is sweet, creamy, and easy to spread once the cake has cooled completely.
How to Make It Step-by-Step
Step 1: Heat the oven to 350°F (175°C), then prepare a 13 x 9-inch baking pan. Grease and flour the pan thoroughly, or line it with parchment so the finished cake can be lifted out more easily.
Step 2: Add the flour, granulated sugar, unsweetened cocoa, baking soda, and salt to a large mixing bowl. Whisk until the cocoa is evenly distributed and no visible pockets of baking soda or salt remain.
Step 3: In a separate bowl, beat the mayonnaise, water, eggs, and vanilla extract until blended. The mixture may look creamy and loose, which is exactly what you want before combining it with the dry ingredients.
Step 4: Pour the wet mixture into the bowl of dry ingredients. Stir just until the batter is smooth and no dry streaks remain, taking care not to overmix because excessive stirring can make the cake less tender.
Step 5: Fold in the semisweet chocolate chips with a spatula. Use gentle strokes so the chips remain evenly suspended throughout the batter instead of collecting at the bottom.
Step 6: Pour the batter into the prepared pan and spread it into an even layer. Bake for 30–35 minutes, checking the center with a toothpick near the shorter end of the baking range.
Step 7: The cake is ready when the toothpick comes out with a few moist crumbs attached. Do not wait for the tester to be completely dry, because the cake continues to firm as it cools and overbaking can remove its signature moisture.
Step 8: Let the cake cool in the pan for about 10 minutes, then continue cooling until completely cool. A warm cake will soften the frosting and make it difficult to create a smooth layer.
Step 9: Make the frosting by beating the softened butter and cocoa together. Add the milk, confectioners’ sugar, and vanilla gradually, beating until the mixture is smooth and spreadable.
Step 10: Spread the frosting over the completely cooled cake. Slice it into about 12–16 portions and serve at room temperature for the softest crumb and fullest chocolate flavor.
Pro Tips for the Moistest Cake
Choose full-fat mayonnaise for the best texture. Its oil keeps the crumb supple, while its egg content helps the batter hold together and bake evenly.
Do not panic if the batter seems thinner than a typical butter cake batter. The water and mayonnaise are important to the final texture, and the mixture will set into a tender cake in the oven.
Pay close attention during the last few minutes of baking. A toothpick with a few moist crumbs is the ideal signal; a completely clean tester usually means the cake has baked longer than necessary.
For the frosting, softened butter should be pliable but not melted. If it is too firm, the frosting may be lumpy; if it is melted, the finished mixture can become loose and difficult to spread.
When adding confectioners’ sugar, mix gradually to avoid a cloud of sugar and to make it easier to control the consistency. If the frosting seems too thick, the measured milk helps loosen it into a smooth, spreadable topping.
For another quick chocolate treat when you do not need a full pan, try this easy chocolate mug cake. It makes a nice small-batch companion to this generously sized dessert.
Serving and Decorating Ideas
This cake is delicious with nothing more than its cocoa frosting, but a few simple finishing touches can make it especially inviting. Sprinkle a small handful of semisweet chocolate chips over the frosting, or add chocolate curls just before serving.
For a party, cut the cake into small squares and arrange them on a platter. The 13 x 9-inch shape is convenient for sharing, and the sturdy frosting helps each piece look finished without requiring elaborate decoration.
Serve each square with coffee, cold milk, or a scoop of vanilla ice cream. A few fresh berries can add color and a lightly tart contrast to the rich chocolate flavor.
If you are planning a dessert table, balance the deep chocolate cake with something fruit-forward such as this bright rhubarb poke cake. Its tangy flavor offers a refreshing change between bites.
Storage and Make-Ahead Advice
Once frosted, keep the cake covered so the surface does not dry out. It can be served after the frosting has set, and the flavor remains satisfying as the cake rests.
For longer storage, refrigerate the covered cake. Let individual portions sit at room temperature briefly before serving so the frosting softens and the crumb becomes pleasantly tender again.
You can also prepare the cake ahead for a gathering, then frost it after it has cooled completely. Cooling usually takes about 30–45 minutes when combined with the initial rest in the pan, although the exact time depends on the room and pan temperature.
Keep leftover slices well covered and use clean utensils when serving. This simple habit protects the frosting and helps the cake maintain its rich, moist texture.
For another make-ahead dessert with a different flavor profile, consider these tender banana pound cake slices. They are a useful option when you want to offer both chocolate and fruit-based sweets.
Common Questions
Can I taste the mayonnaise? No. The mayonnaise blends into the batter, leaving behind richness and moisture rather than a savory flavor. Cocoa, vanilla, sugar, and chocolate chips define the finished taste.
Why should I avoid overmixing? Stirring only until smooth prevents excess gluten development. This keeps the baked cake soft instead of dense or chewy.
Can I use a different pan? The tested yield is for one 13 x 9-inch cake. A different pan can change the batter depth and baking time, so use the specified pan when possible and rely on the moist-crumb toothpick test.
What if I want more dessert variety? Add a contrasting bar cookie to the serving table, such as these oatmeal bars with white chocolate chips. Their oat texture and white chocolate sweetness pair nicely with dark cocoa cake.
Double Chocolate Mayonnaise Cake: Moist & Decadent
Ingredients
Method
- Heat the oven to 350°F (175°C). Grease and flour a 13 x 9-inch baking pan, or line it with parchment.
- Whisk together the flour, sugar, cocoa, baking soda, and salt in a large bowl.
- In a separate bowl, beat the mayonnaise, water, eggs, and vanilla until blended.
- Add the wet mixture to the dry ingredients and stir just until smooth. Do not overmix.
- Fold in the semisweet chocolate chips, then pour the batter into the prepared pan.
- Bake for 30–35 minutes, until a toothpick inserted in the center comes out with a few moist crumbs.
- Cool the cake in the pan for about 10 minutes, then cool completely before frosting.
- For the frosting, beat the butter and cocoa together. Add the milk, confectioners' sugar, and vanilla gradually, beating until smooth and spreadable, then frost the cooled cake.
Notes
Final Thoughts
This Double Chocolate Mayonnaise Cake proves that a humble pantry ingredient can produce an extraordinarily tender dessert. With a 15-minute prep time, a single 13 x 9-inch pan, and a 30–35 minute bake, it offers an easy route to rich homemade chocolate cake for about 12–16 servings.
Remember the two most important details: use full-fat mayonnaise and remove the cake when the toothpick shows a few moist crumbs. Once the cake cools and receives its smooth cocoa frosting, you will have a soft, chocolate-filled dessert that tastes far more elaborate than the method suggests.
Cut a generous square, pour a glass of milk or coffee, and enjoy this moist, decadent classic while the frosting is creamy and the chocolate chips are still wonderfully tender.