Did I Pass the Litmus Test?: Chocolate-Mocha Marshmallow Cake

I continued baking out of Abigail Dodge's cookbook The Everyday Baker when I needed a cake for an office celebration. I wanted to make a layer cake but didn't have a ton of time. So I decided to try Dodge's Chocolate-Mocha Marshmallow Cake," a two-layer chocolate-mocha cake with marshmallow frosting and chocolate glaze.

The cake should have been pretty straightforward. You cream room temperature butter with sugar, brown sugar, and espresso powder; add eggs; alternately add the sifted dry ingredients (flour, cocoa powder, baking soda, and salt) and sour cream; and add hot water and Kahlúa. As I was in the process of weighing out the dry ingredients before sifting, I realized that I had a problem. The recipe calls for natural cocoa and baking soda. I don't keep natural cocoa on hand -- my stock baking cocoa is Valrhona dutched cocoa powder. The thing about dutched cocoa powder -- which has been treated with an alkalizing agent so that it has a neutral pH, in contrast to natural cocoa powder, which is acidic -- is that it won't react with baking soda in the same way.

I realized that the leavening for the cake might end up totally out of whack, so I made my best guess and substituted 1.5 teaspoons of baking powder for the 1 teaspoon of baking soda listed in the recipe. But then as I finished mixing the batter I realized that I probably should add some baking soda to neutralize the acidic sour cream in the cake, so I also added one-quarter teaspoon of baking soda. I crossed my fingers and divided the batter between two parchment-lined 9-inch pans.
The cakes looked good when I took them out of the oven. I had used bake even strips and the cakes had flat tops that didn't require any leveling. The marshmallow frosting is a variation of Swiss meringue. You start making it by beating egg whites, corn syrup, sugar, and salt in a bowl over a pan of simmering water until the mixture is thick and holds medium-firm peaks. Then you remove the bowl from the heat, add vanilla (I used the scraped seeds from a vanilla bean), and beat the frosting until it holds firm peaks. I filled and frosted the cooled cake layers. The recipe instructs you to chill the frosted cake for an hour before pouring on a chocolate glaze. I was in a rush and so I skipped the glaze. Instead I just sprinkled on some Valrhona crunchy dark chocolate pearls. I covered the cake with a dome, left it out on the counter at room temperature, and called it a night.
The marshmallow frosting remained soft and floppy, so  the cake was a bit messy to cut and serve. I was relieved that the cake texture looked fine -- although it was a touch damp. I thought this cake looked incredibly fun and festive and I received a lot of compliments on it -- but I also thought it looked better than it tasted. The intensely chocolate-coffee flavored cake was a little heavy and the frosting was too sweet for my taste, although I understand why the two are paired together. Of course I have to wonder if the cake crumb would have been lighter and more tender if I had followed the recipe and not just winged the leavening.

This is actually the second time that I've subbed dutched cocoa for natural cocoa recently and gotten away with it. I forgot to mention in my post for Irvin Lin's Pistachio Butter Swirled Brownies that I used Valrhona dutched cocoa powder even though the recipe calls for natural cocoa powder and baking soda -- to no apparent ill effect (I didn't notice my error until after the brownies were already in the oven). I've learned my lesson. Dodge notes that she tested her recipes in The Everyday Baker with Hershey's natural cocoa since it's so readily available. It's also cheap, so I bought a large canister and it's ready and waiting in my kitchen for the next recipe that calls for natural cocoa.

Recipe: "Chocolate-Mocha Marshallow Cake" from The Everyday Baker by Abigail Dodge.