This elegant cake comes from Rose Levy Beranbaum’s, The Baking Bible. I omit the caramel component in the white chocolate buttercream because I believe the the flavors of the bittersweet chocolate and custard are out-shined in the original recipe. I’ve multiplied the custard amount by 1 ½ because it’s delicious and is simply not enough on its own without the caramel…and because I always eat a little of it first.
The custard buttercream can be made a day in advance, but should be prepared at least 3 hours before beginning the cake.
For the Custard:
- 450 g (15.9 oz) Quality white chocolate, chopped
- 225 g (7.95 oz) Unsalted butter plus 213 g (7.5 oz) reserved for completion
- 6 large eggs, room temperature
Melt the butter and chocolate together using the double-boiler method. Stir continuously until creamy and smooth.
In a small bowl, break the eggs up with a whisk, and incorporate them into the melted chocolate. Stir custard continuously with a rubber spatula until it thickens slightly, thermometer should read 160 degrees F/71 degrees C. Remove custard from heat and press through a sieve into a bowl. Place mixture into an ice bath and stir until completely cooled.
Complete the buttercream by beating the remaining butter for about 30 seconds at medium-low speed in a large bowl. Add the custard base to the whipped butter. Beat at medium-high speed until stiff peaks form, about 2 minutes. Cover tightly with plastic wrap and set aside for 2 hours until custard is thickened and spongy. At the 2 hour mark, check its temperature to ensure it is not warmer than 70 degrees F/21 degrees C. If needed, place in an ice bath and stir until cooled. Beat custard until smooth and creamy using an electric mixer at medium-high speed, about 30 seconds.
Refrigerate until ready to assemble cake.
For the Cake:
- 85 g (3 oz) Quality unsweetened chocolate, chopped
- 9 g (2 Tbsp) Dutch-processed cocoa
- ¾ cup (177 ml) Strong, hot coffee
- 242 g (8.5 oz) Sour cream
- 2 tsp (10 ml) Vanilla Extract
- 3 large eggs, room temperature
- 228 g (8 oz) cake flour
- 9 g (2 tsp) baking powder
- 4.1 g (¾ tsp) baking soda
- 4.5 g (¾ tsp) salt
- 170 g (6 oz) unsalted butter
- 1 ½ Tbsp (22 ml) safflower or canola oil
- 350 g (123 oz) sugar
Preheat oven to 350 degrees at least 20 minutes before baking. Prepare two 9 inch round cake pans: coat with shortening, top with parchment rounds, coat with baking spray and flour. For the most even results encircle each pan with cake strips.
Melt the chocolate by microwaving it in intervals on low power; the double boiler method also works here. Set aside chocolate and keep warm.
Whisk the cocoa powder and coffee together in a small bowl until dissolved. Cover, set aside, and keep warm.
In another small bowl, combine the sour cream and vanilla. Again, in another small bowl, lightly whisk the eggs. Set each of these aside.
In a medium bowl, whisk together dry ingredients: flour, baking powder, baking soda, and salt.
Combine the oil and butter in the bowl of an electric mixer. Beat at medium speed until creamy and color lightens, about 45 seconds. Gradually add the sugar continuing at medium speed until mixture becomes fluffy and color turns very light, about 4 minutes.
Next, incorporate the eggs slowly into the fat and sugar mixture. With the mixer and medium-low speed, continue to beat for about 4 minutes. Mixture will lighten in color and texture and will be well blended.
Turn off the mixer to stir in the melted, warm chocolate. Immediately turn mixer back on to low speed and blend to incorporate.
Add the dry ingredients to the bowl of the standing mixer in three additions, alternating with the sour cream mixture in two additions. Keep the mixer on low speed to mix and turn off every so often to scrape the sides and incorporate with a spatula. Once those components are added, gently fold in the warm coffee mixture in four additions until smooth.
Pour batter into prepared pans and bake for 30-40 minutes. An inserted toothpick should come out clean, and the center of cake should spring back when lightly pressed. Cool cakes in their pans on a wire rack for 10 minutes. At the 10 minute mark carefully remove the cakes from their pans and allow to completely cool.
Ensure cake is completely cool before frosting. Once frosted, chill for 30 minutes then apply the ganache:
- 67 g (2.3 oz) sugar
- 40 g (40 ml) water
- 2 tsp (10 ml) corn syrup
- 33 grams (1.2 oz) unsweetened cocoa powder
- 38 g (40 ml) heavy cream
- 2 Tbsp (30 ml) cold water
- 3 g (1 tsp) powdered gelatin
Using a whisk, dissolve the sugar with 40 ml of water in a saucepan over medium heat. Remove from heat and add the corn syrup. Whisk gently to combine then add the cocoa powder. Once everything is smooth and glossy, stir in the cream with a rubber spatula.
Return pan to medium heat. Stirring occasionally, bring mixture to a simmer; bubbles will appear around the edges of the pan. Strain mixture through a sieve into a metal bowl. Allow to cool for 30 minutes.
Meanwhile, bloom the gelatin in cold water. Stir to moisten and let sit for at least 5 minutes. When ready, stir the softened gelatin into the chocolate glaze using a rubber spatula. The gelatin will dissolve completely and the glaze should be streak-free.
Strain into a glass measure and stir gently. When the temperature has reached about 85 degrees F/29 degrees C, pour over frosted cake.