This cake has been quite a while in the making, in a lot of ways. I turned 21 last week, and had decided to make my own cake (it saves me from complaining and turning up my nose and making faces), so I knew I wanted to make something rich, indulgent and chocolate-y.
But I get ahead of myself. The idea for the topping came from over a year ago, in the sleepy back row during lecture for a class called "Science and Cooking" at school. We had a guest lecture that day by Bill Yosses, the White House pastry chef. He had some interesting stories from his work, casually mentioning the chocolate cookies that were Sasha and Malia's favorites, but I'm afraid I found the majority of his presentation thoroughly uninspiring. Mr. Yosses spent the majority of our 90 minutes discussing the history of electricity (which I'm sure did somehow relate to the culinary arts, but I definitely wasn't paying close enough attention make the connection).
The one part I do remember is watching him play with melted sugar, carefully shaping it to make a delicate candy apple. It looked like blown glass, and there was something so beautiful about how ephemeral it was, to be eaten or to melt from the moisture in the air. (You can see him make the apple here).
So the idea of melted sugar decorations had been bumping around in my head for a while, and I thought they would be perfect perched on a cake, especially against the contrast of a chocolate one.
The cake itself has also been waiting to be made for a while. At my desk one October afternoon, I looked up from Pinterest (my go-to form of procrastination, though ModCloth is a close second), turned to my roommate and announced that I really wanted to make a chocolate cake. Helen responded with something like a sad shake of the head at the things that occupy my brain before returning to her physics homework, but despite my preoccupation, the cake never happened last semester.
To be honest, I've always been sort of reluctant to tackle fancy layer cakes. They're hard to photograph, and making even cake layers and smoothing the frosting--and worse, cutting the cake--have always kind of stressed me out. But if not for my birthday, then when?
The chocolate cake is lovely, dense, rich, and extremely chocolate-y. It's simple, and a perfect go-to basic chocolate cake. I thought I had adapted it from Magnolia Bakery's chocolate cake recipe, but as I opened my can of Hershey's cocoa powder to make the cake, lo and behold, there was the almost exact same recipe. (Feel free to go off the Magnolia version, if it makes you feel classier. I promise not to tell!)
However, it's definitely the frosting that steals the show in this cake. The richness of the chocolate (almost a pound of it!) is tempered by the sour cream, which gives it a faint tartness. Fudge-y and smooth, it's almost like frosting your cake with chocolate truffles. Believe me, this is a hundred times better than that awful too-sweet buttercream.
Putting all of these elements together, this cake was definitely worth the wait.
For the Chocolate Cake
2 cups cake flour
¾ cup cocoa powder
1 ½ teaspoon baking soda
1 ½ teaspoon baking powder
½ teaspoon salt
1 ¼ cups granulated sugar
½ cup dark brown sugar
½ cup vegetable oil
1 tablespoon vanilla extract
1 cup buttermilk
1 cup strongly brewed hot coffee
For the Chocolate Sour Cream Frosting
12 ounces good quality bittersweet chocolate, roughly chopped (you can replace some of it with semi-sweet or milk chocolate if you prefer a sweeter, less intense chocolate frosting)
½ cup butter, cubed
2 tablespoons honey
½ cup sour cream
2 tablespoons milk
For the Spun Sugar Decoration (optional)
½ cup granulated sugar
¼ cup water
Preheat the oven to 350 F. Grease and flour two 8-inch round cake pans.
Whisk together the flour, cocoa powder, baking soda, baking powder, and salt. In a separate bowl, mix together the eggs and white and brown sugars until smooth. Mix in the vegetable oil, and then the vanilla extract and buttermilk.
Pour the wet ingredients into the dry and gently whisk until combined. Whisk in the coffee. Pour the batter into the two cake pans (try to distribute it evenly), and bake for 35-40 minutes, or until a toothpick inserted into the center comes out clean. Let cakes cool for an hour, unmold, then let them cool completely.
Make the frosting. Place the chocolate, butter, and honey in a heatproof bowl. Place the bowl over a pot of simmering water (make sure the bottom of the bowl doesn’t touch the water). Stir constantly until the chocolate is melted and smooth.
Take the bowl off the heat, and stir in the sour cream and milk. Let sit for 2-3 minutes, stirring occasionally, until the frosting thickens in consistency and is spreadable.
Place one of the cake rounds, domed side up , onto a cake stand or serving plate, and spread a thick layer of frosting over the top. Place the other cake round, domed side down, on top of the frosting. You can cut off the domes to level the cake layers before assembling them if you wish, but I didn’t find this necessary.
Spread the frosting over the top of the cake, then on the sides. It doesn’t have to be perfectly smooth--frosting swirls give this cake a certain appeal. If the frosting becomes too hard, re-heat it over the water bath, and it will soften again.
When you’re ready to serve the cake, make the spun sugar decoration, if desired. Place the sugar and water in a small saucepan. Gently stir over medium heat until it comes to a bowl. Let boil until the sugar turns a golden color. (Once it begins to boil, stop stirring or the sugar might seize and crystallize).
Let the sugar cool until it thickens slightly. If you insert a fork into the sugar, it should trail thin threads of sugar as you pull it away.
As you wait for the sugar to cool, grease the handles of 4-5 wooden spoons (chopsticks work as well), and tape them to your kitchen sink (or to a countertop) so that the handles are hanging over the sink (or over a newspaper-covered floor).
Dip the fork into the melted sugar and gently flick it back and forth over the spoon handles, trailing sugar threads over the handles. Repeat until you get the desired amount of spun sugar. (If the sugar become too hard, heat it on the stove again until it softens.)
Carefully remove the sugar from the spoon handles and place on top of the cake. Serve immediately. (The spun sugar will melt in a few hours).