Chocolate mayonnaise cake is an old fashioned layer cake that's moist and tender with deep chocolate flavor. It's filled and frosted with the creamiest mocha buttercream ever! It's great for birthdays or Sunday dinners! Instructions for making chocolate mayonnaise sheet cake included.
Grease three 8 -inch cake pans and dust with cocoa.
Melt the chocolate in the microwave just until softened and you can stir it smooth - about 1 minute.
Combine melted chocolate and cocoa in a bowl. Whisk in boiling coffee (or water) and stir until the mixture is smooth. Set aside.
Sift the flour, baking soda, baking powder, and salt into a bowl. Set aside.
With an electric mixer on medium-high speed beat the sugar and the mayonnaise until blended.
Add eggs one at a time, beating well after each. Add the egg yolk.
Beat in the vanilla.
Change to low speed. Add the dry ingredients in four additions, alternating with the chocolate mixture.
Beat well after each addition.
Divide batter evenly among the cake pans.
Bake about 30 minutes or until a cake tester comes out clean.
Cool cake for 10 minutes in pans.
Loosen cakes from sides of pans, turn out, and cool completely.
In a bowl of stand mixer fitted with paddle attachment beat the butter on medium speed about 6 minutes or until pale and fluffy.
Sift together the confectioners' sugar and cocoa powder.
Reduce mixer speed to low.
Add the confectioners' sugar mixture, beating until well blended.
Continue beating on low and add the coffee, sour cream, vanilla, and salt.
Beat 1 minute.
Increase the speed to medium and whip for 2 minutes.
Add the melted chocolate and beat until smooth, about 2 minutes more.
For sheet cake
Follow instructions through step three.
Grease and flour a 13x9-inch baking dish.
Pour the batter in the baking dish and smooth top.
Bake for 30 to 35 minutes at 350°. Start checking for doneness at 25 minutes just to be on the safe side.
Cool completely in pan and frost with your favorite frosting.
Make the cake exactly like the recipe the first time you make it - don't make substitutions. After that you can adjust as you desire.
Make sure all ingredients are at room temperature before you begin.
I dust my cake pans for chocolate cake with cocoa. That way any cocoa that clings to the crust of the cake it the same color as the cake. Just do it the same way you do with white flour...spoon a little into a greased pan and shake it around until it covers all surfaces then dump it out.
If you've had a problem with cakes sticking to the pans in the past then place a round of parchment paper in the bottom of the pans and grease it then dust with cocoa. The bottom will come loose without a problem and you can just peel the parchment paper off after it's done.
Don't scoop the flour from the container when measuring. Use a spoon and spoon the flour lightly into the measuring cup. Level it off with the flat edge of a butter knife.
Don't use reduced fat, olive oil, canola oil, fat free, or other mayonnaise variation. Use the old fashioned, full fat mayo - I suggest Hellman's.
Pour the batter into the pans and bake immediately. Once the leavening is wet it starts to lose strength and your cake won't rise as well.
Don't over bake your cake. Check it by inserting a toothpick into the center of the cake. If the toothpick comes out clean with a few crumbs clinging to it the cake is ready..
Let chocolate mayonnaise cake layers rest in the pans about 10 minutes after removing them from the oven.
Place a couple of thin dowels or straws through the stacked cake when you are frosting the sides and top - this will keep it from sliding around. Just remove them and smooth the top before serving.