This moist chocolate cake is one of those special cake mixes that is made with simple ingredients, but the signature being mayonnaise! The first time you taste a bite, it will quickly become your new favorite chocolate cake.
Preheat oven to 350°F. Spray a 9x13 baking pan with nonstick cooking spray and set aside.
Whisk together the flour, ½ cup cocoa powder, granulated sugar, baking soda, and salt.
In a separate bowl, combine the milk, eggs, mayonnaise, and vanilla extract.
Begin stirring the wet ingredients into the dry ingredients (mixture will be very thick). Gradually pour the hot water over the mixture and continue stirring to form a smooth batter.
Transfer cake batter into the prepared baking dish.
Bake for 40-45 minutes, until a toothpick inserted in the center of the cake comes out with a few moist crumbles.
Allow cake to cool completely.
To make the frosting, beat together the butter, vanilla, and cocoa powder until smooth and glossy. Rotate adding the powdered sugar and heavy cream until all ingredients have been incorporated and the frosting is smooth and fluffy.
Spread the frosting over the cooled cake. Cut into squares and serve.
Notes
Storage: Cover with plastic wrap and store in the refrigerator for up to 7 days. Freeze for up to 3 months.Notes:Hot water is a traditional technique used to help break down dry ingredients in a cake batter. It also helps to break down the cocoa powder and develop the chocolate flavor - you’ll often see this technique specifically in chocolate cake recipes.The frosting is technically a doubled recipe - which gives you that nice, thick luscious layer of frosting. You can halve the frosting recipe and still have plenty to cover the top of the cake, but a thinner layer of frosting.The mayonnaise adds moisture to the cake and substitutes for oil or butter. If you do not have eggs, you can simply leave them out of the recipe. Keep everything else as is. The cake will turn out moist and delicious but slightly recessed through the middle.Some mayonnaise cakes skip eggs, oil, and milk. I found this version to be more crumbly. The milk really does add some binding to hold the cake together with a nice moist crumb. You can substitute buttermilk for 2% milk. We used whole milk.