Description
This rich and fudgy Chocolate Mayonnaise Sheet Cake combines the unique moisture of mayonnaise with deep cocoa flavors and a luscious chocolate frosting. Perfectly baked in a 9x13-inch pan, this dessert is easy to make and serves 12 people, offering a moist, tender crumb and decadent chocolate experience.
Ingredients
Scale
Cake
- 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
Frosting
- 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
Instructions
- Prepare the pan and oven: Preheat the oven to 350°F (180°C). Brush a 9x13-inch sheet pan with butter and set aside.
- Mix dry ingredients: In a medium bowl, stir together the flour, cocoa powder, baking powder, baking soda, and salt until evenly combined, then set aside.
- Dissolve coffee powder: In a glass measuring cup, mix instant coffee powder with hot water until dissolved and set aside.
- Beat mayonnaise and sugars: Using an electric mixer, beat mayonnaise with white and brown sugars in a large bowl until pale and creamy.
- Add eggs and vanilla: Add eggs one at a time, beating well after each addition. Scrape the bowl sides periodically. Mix in vanilla extract thoroughly.
- Combine dry and wet ingredients: Add the dry ingredients in three parts alternately with the coffee mixture in two parts, beating well after each addition. The batter should be neither stiff nor runny.
- Bake the cake: Pour the batter into the prepared pan and bake for 30 minutes or until a toothpick inserted into the center comes out with moist crumbs. Let the cake cool completely before frosting.
- Melt chocolate for frosting: In a microwave-safe bowl, melt chopped chocolate in 20-second intervals, stirring between each, until smooth. Let cool slightly.
- Cream butter and sugar: Beat butter until creamy and fluffy. Gradually add powdered sugar starting on low speed, then increase to high and beat for 2 to 3 minutes.
- Add cocoa powder: Beat cocoa powder into the frosting, scraping bowl sides occasionally for smoothness.
- Add cream and melted chocolate: Mix in heavy cream and cooled melted chocolate, beating until well combined. Refrigerate frosting for 10 minutes before using.
- Frost the cake: Spread the frosting evenly over the cooled cake, creating swirls with a spatula or spoon.
- Serve and store: Slice and serve. Cover unfrosted cake with plastic wrap and store at room temperature for 1 day or refrigerate for up to 7 days. Frosted cake can be refrigerated for 3 days; bring to room temperature before serving to soften frosting.
Notes
- Brush the baking pan with butter to prevent sticking.
- Use Dutch processed cocoa powder for the best chocolate flavor.
- Dissolving instant coffee in hot water enhances the chocolate depth without adding coffee flavor.
- Beat mayonnaise and sugars until pale and creamy to ensure a moist cake texture.
- Scrape down bowl sides during mixing to incorporate all ingredients evenly.
- Check the cake with a toothpick; it should come out with moist crumbs, not wet batter.
- Allow melted chocolate to cool slightly before adding to frosting to prevent melting the butter.
- Refrigerate frosting briefly to thicken it for easy spreading.
- Let frosted cake come to room temperature before slicing to soften the frosting for clean cuts.
Nutrition
- Serving Size: 1 slice (approx. 1/12 of cake)
- Calories: 450 kcal
- Sugar: 38 g
- Sodium: 220 mg
- Fat: 28 g
- Saturated Fat: 9 g
- Unsaturated Fat: 14 g
- Trans Fat: 0 g
- Carbohydrates: 48 g
- Fiber: 4 g
- Protein: 5 g
- Cholesterol: 55 mg
