1 1/2 tablespoons unsweetened Dutch-process cocoa
1 3/4 cups milk
3/4 cup sugar
1 ounce bittersweet chocolate, roughly chopped
2 tablespoons cornstarch
1 tablespoon cold water
1/4 tablespoon salt
1 teaspoon vanilla
2 tablespoons unsalted butter
Butter and flour for preparing the pans
1/2 cup unsweetened Dutch-process cocoa
3 tablespoons boiling water
2 ounces bittersweet chocolate, chopped
3/4 cup milk
2 cups sugar
2 sticks butter, slightly softened
4 eggs, separated
2 teaspoons vanilla
2 cups flour
1 teaspoon baking powder
1 teaspoon salt
1 teaspoon baking soda
12 ounces bittersweet chocolate, roughly chopped
3/4 cup unsalted butter, cut into chunks
1/2 cup hot water
1 tablespoon corn syrup
1 tablespoon vanilla
- Start by making the filling: Put the cocoa into a small saucepan, pour in the milk and place over medium-low heat. Add the sugar and chocolate and mix a few times to combine. Dissolve the cornstarch in the cold water to make a smooth paste. Whisk the cornstarch paste into the water and chocolate mixture, add the salt and slowly bring the mixture to a boil, stirring constantly. Boil for one minute, stirring, until mixture looks thick.
- Remove the pan from the heat and immediately whisk in the vanilla and the butter. Let mixture cool for 5 minutes, then transfer the mixture to a bowl, cover and refrigerate until cool. (Pudding will continue to thicken as it cools.)
- Make the cake: Preheat the oven to 375 degrees; butter and lightly dust two 8-inch round cake pans with flour, set aside.
- Place the cocoa in a small bowl and whisk in the boiling water to form a crumbly paste. Combine the chocolate and milk in a saucepan set over medium heat. Stir frequently as the mixture warms and the chocolate melts, about 3 minutes. Remove from heat. Whisk a small amount of the heated chocolate milk into the cocoa paste and then whisk the cocoa mixture into the milk mixture. Return to heat, stir for one minute until smooth, remove and cool until tepid.
- Meanwhile, using an electric hand mixer, cream the sugar and butter together in a large bowl. Beat in the egg yolks one at a time, then add the vanilla. Slowly add the chocolate mixture and mix to combine.
- Combine the flour, baking powder, salt and baking soda. Using a rubber spatula, slowly add the flour mixture to the chocolate mixture. Clean your mixer beaters well with cold water and dry thoroughly. In another bowl, whip the egg whites on medium-high until they form soft peaks. Using a rubber spatula, gently fold the egg whites into the batter.
- Divide the batter between the two prepared cake pans. Bake for 40-45 minutes, until tops just spring back when pressed (Don’t overbake, or the cake will be dry.) Cool on a rack in the pans for 15 minutes, then gently remove the cakes from the pans and continue to cool.
- Make the frosting: In a double boiler, melt the chocolate, stirring often. Remove from heat and whisk in the butter, one chunk at a time, returning to heat if necessary to melt the butter.
- Whisk in the hot water all at once and stir until smooth. Whisk in the corn syrup and the vanilla until glossy and smooth. Refrigerate for 10-15 minutes (but not more, or it will harden) before using.
- Assemble the cake. Use a sharp knife to slice each cake into two disks to form four layers. Set one layer aside. Place one layer on a cake round or plate. Generously swath the layer with pudding. Add the second layer and repeat. Add the third layer. Quickly apply a layer of frosting to the top and the sides of the cake and refrigerate for 10 minutes. (You can anchor the cake with toothpicks if it’s sliding). Meanwhile, crumble the remaining cake layer. Apply a second layer of frosting to the cake, sprinkle liberally with crumbs and serve within 24 hours. Store cake in fridge.