Jill O'Connor's Chocolate Mayonnaise Layer Cake with Melted Chocolate Bar Frosting

You probably have a great job. At least you think you do. But you're not Jill O'Connor. You see, Jill O'Connor is a pastry chef who writes dessert cookbooks for a living. She's written six--the latest, published in 2009, is Sticky, Chewy, Messy Gooey Treats for Kids. And next month, number seven debuts: Cake, I Love You: Decadent, Delectable, and Do-able Recipes. In between her books, Jill develops recipes and writes for a variety of publications, including The San Diego Union-Tribune's food section.

Imagine a life of making sweet treats that bring joy to others. That's pretty much Jill's world. And, knowing Jill as I do, it all comes from the heart.

Jill invited me to her house recently to make one of the cakes in the book. I figured that since San Diego Foodstuff is celebrating its 10th anniversary this year I needed as much cake as possible to make that feel real. Imagine the wealth of choices I had--from her Coconut Fudge Snow-Ball to Blood Orange Ricotta Pound Cake--Jill offered me a few choices.

This Chocolate Mayonnaise Cake with Melted Chocolate Bar Frosting was clearly the winning choice. Chocolate. Chocolate with Mayonnaise. And Chocolate Bar Frosting? Whew!

Sounds decadent and difficult, right? In fact, yes, it is decadent if you adore chocolate. But, says Jill, "This is what I would call an after-school cake." Meaning it's accessible to the home baker.

Now Jill writes a great recipe. Everything is clear and straightforward. But it was wonderful to be with her in her kitchen in Coronado to pick up some of her cake making and layer cake frosting tips. Let's face it. Baking a cake can be pretty easy if you follow the recipe. But the skill involved in making the layers even and then frosting it? That's an art. And I wanted to learn that art from the master.

As Jill set up her Kitchen Aid stand mixer and began to mix the liquid cake ingredients she gave me her first tip: always add sugar slowly to eggs. Why? Doing this in reverse will burn the eggs. Who knew?

Now you may be wondering about the mayo and why it's in the recipe. This is actually a pretty common ingredient going back to the 1930s and 40s when butter and eggs were being rationed because of World War II. It basically was an accessible and economical fat substitute for baking.

Another tip Jill employs is adding a bit of coffee to chocolate. You may already do this or have heard about this trick. No, you won't get coffee flavor with such a small amount, but what it does is enhance the flavor of the chocolate.

Let's talk cocoa for a moment. Be sure to read the label when you reach for a container. What you do not want is Dutch processed cocoa. Here's why, according to Jill: Baking soda, which is in this recipe as a leavening agent, needs something acidic to make it work to activate its leavening power. If you add too much acid (such as what's in Dutch processed cocoa) you'll get a salty soapy taste. Instead, Jill uses Hersey's Dark Special Process cocoa.

Once you have mixed the batter, if it seems too thick, Jill says you can thin it with boiling water--just a little at a time to come to the right consistency. You also want to eliminate any lumps, so whisk until they're all gone.

Now, you could bake this as a sheet cake, but it makes for a gorgeous layer cake. So, you'll want two round cake pans, sprayed with Pam or some other nonstick cooking spray. Then you'll line the bottom with parchment paper. Split the batter evenly between the two pans and give them some sharp taps to eliminate any bubbles. If you're really concerned about whether you've evenly divided the batter, go ahead and weigh each filled pan on a digital scale.

Okay, now it's time to focus on the frosting. If you're the type who plans ahead, Jill suggests making it the day before so it can sit and thicken naturally overnight.

Jill calls this a chocolate bar frosting, but she's actually not using chocolate bars. "It's chocolate bar like because I use milk chocolate chips," she explains.

The frosting calls for powdered sugar. You can add more than what's listed in the recipe if you want a firmer texture and sweeter flavor.

The recipe for the frosting is pretty straightforward. But what you really want to know is how to get it on the cake so that you have something irresistibly gorgeous and not like you're five-years-old. This is how you do that.

First, place the cake on something higher than the counter, like a cake plate but it could also be a large upside down mixing bowl--and the cake itself should be on a cake board, which is stiff and lets you more easily maneuver it. You can find cake boards at Michael's.

Now, using an offset spatula, you spread on a "crumb coat." Basically, it's a thin coat of frosting that covers the crumbs "like spackle," Jill says.

Then it's the moment of truth. You glide on that luxuriant second coat of frosting all over the cake.

Still listing a bit? Take a cue from Jill, who does experience this from time to time. "Toss on chocolate sprinkles," she says. "It's like a cake bra. It helps hold it in place and creates a visual camouflage."

That's just what she did with our cake. And it was the source of one last trick. To put the sprinkles on the cake, place them in a large bowl. Carefully hold the cake over the bowl by the cake board. Using your free hand, grab a handful of sprinkles and gently press into the side of the cake, letting the excess fall back into the bowl. Turn the cake little by little and repeat until you've covered the sides with the sprinkles.

That's it! Oh, except for digging in. The cake itself is a marvel. It's moist and slices beautifully. It has the most sumptuous chocolate flavor--not too sweet but definitely satisfying for the sweet tooth. Make it for your kids to enjoy after school or impress your friends at a dinner party.

Cake, I Love You will be published on May 23. It's available for pre-order on Amazon.

Old Fashioned Chocolate Mayonnaise Cake with Melted Chocolate Bar Frosting
From Jill O’Connor and her book Cake, I Love You: Decadent, Delectable, and Do-able Recipes

I am always looking for an easy-to-bake cake that’s good enough to make an ordinary Wednesday feel special. This chocolate cake is luxuriously rich, yet with a surprisingly light texture. The batter is versatile and sturdy enough to be baked in a 9x13-inch pan for an everyday celebration, or into two 9-inch round cake pans if the occasion calls for a layer cake instead. Mayonnaise cakes were popularized in the late 1930’s by Hellman’s Mayonnaise as a more economical substitution for butter and eggs. Since mayonnaise is simply an emulsion of eggs and oil with a dash of vinegar, it works beautifully. This cake is tasty enough to eat plain, but I prefer to slather it with Melted Chocolate Bar Frosting; it takes 5 minutes to whip together from pantry staples and all you really need is a bowl, a wooden spoon, and a strong arm. 

Yield: One 9- by-13-inch cake, or 9-inch round double-layer cake

Cake
2 cups all purpose flour
¾ cup natural cocoa powder
1 teaspoon baking powder
½ teaspoon baking soda
¼ teaspoon salt
2 cups granulated sugar
2 eggs
1 cup mayonnaise (do not use low-fat)
2 teaspoon vanilla extract
1 1/2 teaspoon instant espresso powder or coffee powder
1 1/3 cups boiling water

Melted Chocolate Bar Frosting:
1 cup semisweet chocolate chips
1 cup milk chocolate chips
½ cup unsalted butter
1 cup sour cream
1 teaspoon vanilla
Large pinch fine sea salt
2 to 3 cups confectioners’ sugar, sifted

Heat the oven to 350°F. Spray a metal 9- by-13 inch sheet pan (or two 9-inch round cake pans with nonstick cooking spray. (If using round cake pans, line the bottom of each pan with parchment paper.)

In a medium bowl, sift together the flour, cocoa powder, baking powder, baking soda, and salt.

In the bowl of a stand mixer fitted with the paddle attachment, beat the sugar and eggs together at medium-high speed until light and fluffy, 3 to 4 minutes.  Beat in the mayonnaise and the vanilla until smooth.

Lower the mixer speed to its lowest speed and beat in 1/2 the dry ingredients just until combined. Stop the mixer and scrape down the sides of the bowl.

In a small bowl, mix together the espresso powder with the boiling water.  Add 1/2 of the espresso mixture to the batter and beat on low speed just until the batter is smooth, about 5 to 10 seconds. Add the remaining dry ingredients and beat just until combined.  Beat in the remaining espresso and beat just until smooth. The batter will be somewhat thin.

Scrape the batter into the prepared pan (s) and bake 22 to 25 minutes until a wooden skewer inserted in the middle of the cake comes out clean. Transfer the pan to a wire rack and let cool completely.

For the frosting: In a large, microwave-safe bowl, combine the semisweet and milk chocolate chips with the butter.  Heat on high power for 1 minute. Stir together until the butter and chocolates are completely melted and smooth.  If not completely melted after 1 minute, heat again in 15-second increments, stirring until smooth. Use a large balloon whisk or a wooden spoon and stir in the sour cream.  Beat in add 2 cups [xx g] confectioners’ sugar, just until smooth and spreadable.  If a thicker, sweeter frosting is desired, beat in an additional cup of sugar.

Spread the top of the cooled cake with the Melted Chocolate Bar Frosting. Cut into squares and serve. Cover pan tightly with plastic wrap or foil, and store at room temperature. The cake will stay fresh for about 2 days.  (For layer cake: place one layer on a cake stand and frost the top with about 1 cup frosting. Top with second layer and spread the remaining frosting on the top and around the sides of the cake.)

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