Two-Layer Chocolate Cake with Chocolate Mousse & White Buttercream
In the spring of 2012, my kitchen looked a lot like this on a daily basis.
I was getting married to Alex in six months, and I had decided it would be a fun project to make my own wedding cake. I’d always been the one who baked banana bread, brownies, and cookies for colleagues, the friend who brought cupcakes and hosted peanut noodle buffets.
And so, though I’d discovered an allergy to many of the contemporary wedding traditions I was finding in my pinterest deep dives, I could hardly throw out the cake with the wedding: If small milestones compelled me to take out the mixing bowl, then clearly this grandiose ceremony mandated six cake pans, a cake turntable, and approximately 1407 grams of chocolate.
Nobody recommended this: not cake greats Silvia Weinstock and Ron Ben Israel, not the Institute of Culinary Education instructor I emailed for advice, not even the very sweet and talented Yossi Arefi, though she was supportive of the idea. My mom, always in favor of a good DIY, was on board.
So there I was, in the kitchen, thinking about dresses and flowers and cake. I was also browsing CakeWrecks, reading up on bleak superstitions (“The bride who bakes her own cake is asking for trouble”), considering the cobwebs on jilted Miss Havisham’s cake layers, and learning that a profession called cake chauffeuring existed.
In addition to contrariness, one of the reasons I was interested in baking my wedding dessert was Alex’s aversion to dairy. Though I knew our cake had to be covered in a bonafide buttercream, white like the wedding dress, I thought that if the entire contents of the interior did not contain milk, cream, or butter, maybe Alex and I could more easily pose for the photographer in the midst of shoving big bites of cake into each other’s mouths. I mixed and matched layers and fillings that didn’t contain dairy and icings that did. In my trials, I discovered that if you baked chocolate cake with olive oil, the result was fruity and moist, and that if you whipped melted chocolate with water, a fine mousse emerged. Together, these became the core of an excellent cake.
I covered that cake in a white buttercream, and the effect of the contrast was dramatic. Here’s what the inside of the wedding cake would have looked like–if I’d gone through with my plan.
As it turns out, transportation is the homemade cake killer. To bake a cake is one valiant act, but to transport it, supported, to the venue, then finish icing and decoration while you–if you are the bride–also attempt to set your curls and rouge your cheeks without winding up covered in buttercream.
And so in the end, Betsy of Nine Cakes made us the most extraordinarily beautiful and delicious cake. Half the tiers were dairy-free chocolate on chocolate, like this cake, and half were pumpkin with maple frosting. (I recommend Nine Cakes you’re in NYC and in need of excellent cake.)
But two years later, I realized I had developed a really good cake that no one but me ever got to try. Here, I’ve re-thought the recipe as a two-layer confection for a more normal occasion, like a birthday. You won’t need 1407 grams of chocolate. But you will satisfy the butter-lovers and butter-haters without making a big thing of it.
For the cake:
Olive oil and flour for the pan
1 cup natural cocoa powder (Dutch is fine too)
2 teaspoons vanilla extract
1 teaspoon almond extract
2 cups all-purpose flour
1/2 teaspoon salt
1/2 teaspoon baking soda
6 large eggs
2/3 cup olive oil
2/3 cup safflower oil
2 2/3 cups sugar
For the filling:
3/4 cup (6 ounces) brewed coffee
8 ounces chocolate, around 70% (or use 1 cup chocolate chips)
pinch of salt
For the buttercream:
1 1/3 cups sugar
4 sticks unsalted butter, at room temperature
1/8 teaspoon salt
1/2 teaspoon vanilla
Make the cakes: Preheat the oven to 325°F. Generously oil two 9-by 2-inch springform cake pans (or a 9-inch cake pan without springform) with olive oil and line the bottom of the pan with parchment or waxed paper. Oil the paper too.
Bring 1 cup of water to boil. Meanwhile, whisk the cocoa powder to break up lumps. Using a spoon or spatula, stir 3/4 cup of the boiling water into the cocoa until it’s smooth and glossy (if the mixture is very thick, you can add water by the tablespoon until you have a paste). Stir in the vanilla and almond extracts. Set aside to cool slightly. In another small bowl, mix together the flour, salt, and baking soda and set aside.
In a large mixing bowl, combine the eggs, oils, and sugar. Using the beaters of a handheld or standing mixer, or your very strong arm, beat on medium-high speed thickened and lightened, about 2 minutes.Reduce the speed to low and add the cocoa mixture until it’s well combined, scraping down the sides of the bowl. Gradually mix in the dry ingredients until just combined, scraping down the sides of the bowl.
Pour the batter into the prepared cake pans and bake in the center of the oven until a toothpick comes out with a few moist crumbs clinging to it but with no wet batter, 35 to 40 minutes. Put the pan on a rack and carefully run an offset spatula or paring knife around the inside edge to release the cake. Let cool for 10 minutes in the pan. Using a second rack to sandwich the cake pan, and flip the pan over. Carefully loosen and lift the pan from the cake, then gently peel off and discard the paper liner, and let the cake cool completely.
Make the filling: Pour the coffee into a saucepan. Then, over medium-low heat, whisk in the chocolate until you have a smooth sauce. Pour the sauce into a small metal bowl and set it into a second, larger bowl that’s filled with ice cubes. Whisk the sauce, watching as it starts to thicken, 3 to 6 minutes, then keep whisking until the sauce has become a spreadable, mousse-like consistency. However, be careful not to over-mix or the mousse will be grainy. Food52 has advice to troubleshoot if anything goes wrong.
Place one layer on a cake plate. Pile the mousse on top. Spread to the edges, then set the second layer, top-side down, on the mousse. Place in the fridge while you make the buttercream.
To make the buttercream: Combine the eggs and sugar in a heatproof bowl–metal works great–and set it over a pot of simmering water. Whisk constantly but not too hard, until the egg-sugar mixture is warm (a drop on the inside of your wrist should feel hot but not burning). Be careful not to curdle it. If you’re using a thermometer, you want it to read 160°F.
Remove from the heat and beat on high speed using a handheld or electric mixer (I wouldn’t recommend doing this by hand). After about 5 minutes, it should have increased in volume and be light, airy, and cool. Turn the mixer to medium and add the butter a few tablespoons at a time, mixing until incorporated. At points, the icing may look curdled. When all the butter is in, whip ’til fluffy, then you’re ready to frost.
**If you would like to make the icing ahead of time, you can, but you will need to store it in the fridge and then let it come to room temperature, a process that takes several hours, before possibly re-whipping it. I’m not sure this is worth the work, but now you know!
Take the cake from the fridge, and spread a thin crumb coat over the whole cake. This is to seal in the chocolate. Do your best not to smear the chocolate filling too much, but don’t worry if it leaks out into the buttercream (that’s what the crumb coat is for!). Place the crumb-coated cake in the fridge for about 20 minutes, then remove and use the rest of the frosting to finish icing the cake. Store at room temperature for a few hours, or in the fridge for longer.