Daring Bakers: Opera Cake

This month the Daring Baker Challenge was for an Opera Cake, a nutty sponge cake with layers of buttercream and mousse, topped off with a silky glaze. It seemed a little complicated with all the different parts, but we were also given a lot of latitude in the flavoring of the different components.

I made the cake with ground almonds. The recipe called for ground blanched almonds, but Trader Joes almond meal isn't made from blanched almonds so the cake was a little darker than it should have been. It tasted great though, and G really like it too.

For the buttercream filling and syrup for brushing on the cake, I decided to do lemon. I added 2 Tbsp lemon juice to the syrup and 2 Tbsp juice and grated zest to the buttercream. The buttercream came together really well, I've learned to really wait for the eggs/sugar mix to cool down before adding the butter. I really liked the flavor and texture of the buttercream too, I may have to make this one again.

For the mousse layer on top, I wanted strawberry flavor. I melted the white chocolate with some cream first. It ended up separating but a little bit more cream made it smooth. I sliced up 1 cup of strawberries and then mashed them a bit with a potato masher so there would still be pieces of strawberries. I stirred this into the white chocolate. Now, white chocolate is not white, it is more yellow in color and after stirring the strawberries in, it wasn't a very pretty color. But, I went ahead and whipped up the cream and then folded it into the white chocolate/strawberry mix. The color definitely improved and it tasted good too. I think next time I would use less white chocolate though, it is very sweet.

Assembling the cake was fairly straight forward. One layer of cake, then buttercream, another layer of cake, then the rest of the buttercream. At this point I came up with the idea of adding blueberries to this layer. This seemed like a good idea, but the buttercream wasn't very thick so the blueberries stuck up and the two layers didn't hold together as they should. Next time I would add some sweetened whipped cream or mousse to this layer. On the very top I put the strawberry mousse. For the glaze on top I melted less white chocolate that what was in the recipe but as it cooled, it got really thick. I was hoping for a thin layer of glaze but I ended up with a thick, not very smooth layer. Next time I would add more cream to thin it out a bit.

I took the cake to a small get together and everyone said that it tasted good. I wished it looked a little better, next time I will trim the side and cut it into smaller pieces.

Opera Cake Recipe:

For the joconde

(Note: The joconde can be made up to 1 day in advance and kept wrapped at room temperate)

What you’ll need:

• 2 12½ x 15½-inch (31 x 39-cm) jelly-roll pans[1]
• a few tablespoons of melted butter (in addition to what’s called for in the ingredients’ list) and a brush (to grease the pans)
• parchment paper
• a whisk and a paddle attachment for a stand mixer or for a handheld mixer
• two mixing bowls (you can make do with one but it’s preferable to have two)

Ingredients:

6 large egg whites, at room temperature

2 tbsp. (30 grams) granulated sugar

2 cups (225 grams) ground blanched almonds[2]

2 cups icing sugar, sifted

6 large eggs

½ cup (70 grams) all-purpose flour

3 tbsp. (1½ ounces; 45 grams) unsalted butter, melted and cooled

1. Divide the oven into thirds by positioning a rack in the upper third of the oven and the lower third of the oven.

2. Preheat the oven to 425^◦F. (220^◦C).

3. Line two 12½ x 15½- inch (31 x 39-cm) jelly-roll pans with parchment paper and brush with melted butter.

4. In the bowl of a stand mixer fitted with the whisk attachment (or using a handheld mixer), beat the egg whites until they form soft peaks. Add the granulated sugar and beat until the peaks are stiff and glossy. If you do not have another mixer bowl, gently scrape the meringue into another bowl and set aside.

5. If you only have one bowl, wash it after removing the egg whites or if you have a second bowl, use that one. Attach the paddle attachment to the stand mixer (or using a handheld mixer again) and beat the almonds, icing sugar and eggs on medium speed until light and voluminous, about 3 minutes.

6. Add the flour and beat on low speed until the flour is just combined (be very careful not to overmix here!!!).

7. Using a rubber spatula, gently fold the meringue into the almond mixture and then fold in the melted butter. Divide the batter between the pans and spread it evenly to cover the entire surface of each pan.

8. Bake the cake layers until they are lightly browned and just springy to the touch. This could take anywhere from 5 to 9 minutes depending on your oven. Place one jelly-roll pan in the middle of the oven and the second jelly-roll pan in the bottom third of the oven.

9. Put the pans on a heatproof counter and run a sharp knife along the edges of the cake to loosen it from the pan. Cover each with a sheet of parchment or wax paper, turn the pans over, and unmold.

10. Carefully peel away the parchment, then turn the parchment over and use it to cover the cakes. Let the cakes cool to room temperature.

For the syrup

(Note: The syrup can be made up to 1 week in advance and kept covered in the refrigerator.)

What you’ll need:

• a small saucepan

Ingredients:

½ cup (125 grams) water

⅓ cup (65 grams) granulated sugar

1 to 2 tbsp. of the flavouring of your choice (i.e., vanilla extract, almond extract, cognac, limoncello, coconut cream, honey etc.)

1. Stir all the syrup ingredients together in the saucepan and bring to a boil.

2. Remove from the heat and let cool to room temperature.

For the buttercream[3]

(Note: The buttercream can be made up to 1 month in advance and packed in an airtight container. If made way in advance, you can freeze the buttercream. Alternatively you can refrigerate it for up to 4 days after making it. To use the buttercream simply bring it to room temperature and then beat it briefly to restore its consistency.)

What you’ll need:

• a small saucepan
• a candy or instant-read thermometer
• a stand mixer or handheld mixer
• a bowl and a whisk attachment
• rubber spatula

Ingredients[4]:

1 cup (100 grams) granulated sugar (Used to say 2 cups but should be 1 cup)

¼ cup (60 grams) water (Used to say ½ cup but should say ¼ cup)

seeds of one vanilla bean (split a vanilla bean down the middle and scrape out the seeds) or 1 tbsp. pure vanilla extract[5]

1 large egg

1 large egg yolk

1¾ sticks (7 ounces; 200 grams) unsalted butter, at room temperature (Used to say 1¾ cups of butter but it should be 1¾ sticks).

flavouring of your choice (a tablespoon of an extract, a few tablespoons of melted white chocolate, citrus zest, etc.)

1. Combine the sugar, water and vanilla bean seeds or extract in a small saucepan and warm over medium heat just until the sugar dissolves.

2. Continue to cook, without stirring, until the syrup reaches 225^◦F (107^◦C)[6] on a candy or instant-read thermometer. Once it reaches that temperature, remove the syrup from the heat.

3. While the syrup is heating, begin whisking the egg and egg yolk at high speed in the bowl of your mixer using the whisk attachment. Whisk them until they are pale and foamy.

4. When the sugar syrup reaches the correct temperature and you remove it from the heat, reduce the mixer speed to low speed and begin slowly (very slowly) pouring the syrup down the side of the bowl being very careful not to splatter the syrup into the path of the whisk attachment. Some of the syrup will spin onto the sides of the bowl but don’t worry about this and don’t try to stir it into the mixture as it will harden!

5. Raise the speed to medium-high and continue beating until the eggs are thick and satiny and the mixture is cool to the touch (about 5 minutes or so).

6. While the egg mixture is beating, place the softened butter in a bowl and mash it with a spatula until you have a soft creamy mass.

7. With the mixer on medium speed, begin adding in two-tablespoon chunks. When all the butter has been incorporated, raise the mixer speed to high and beat until the buttercream is thick and shiny.

8. At this point add in your flavouring and beat for an additional minute or so.

9. Refrigerate the buttercream, stirring it often, until it’s set enough (firm enough) to spread when topped with a layer of cake (about 20 minutes).

For the white chocolate ganache/mousse (this step is optional – please see Elements of an Opéra Cake)
(Note: The mousse can be made ahead and refrigerated until you’re ready to use it.)

What you’ll need:

• a small saucepan
• a mixer or handheld mixer

Ingredients:

7 ounces white chocolate

1 cup plus 3 tbsp. heavy cream (35% cream)

1 tbsp. liquer of your choice (Bailey’s, Amaretto, etc.)

1. Melt the white chocolate and the 3 tbsp. of heavy cream in a small saucepan.
2. Stir to ensure that it’s smooth and that the chocolate is melted. Add the tablespoon of liqueur to the chocolate and stir. Set aside to cool completely.
3. In the bowl of a stand mixer, whip the remaining 1 cup of heavy cream until soft peaks form.
4. Gently fold the whipped cream into the cooled chocolate to form a mousse.
5. If it’s too thin, refrigerate it for a bit until it’s spreadable.
6. If you’re not going to use it right away, refrigerate until you’re ready to use.

For the glaze
(Note: It’s best to make the glaze right when you’re ready to finish the cake.)

What you’ll need:

• a small saucepan or double boiler

Ingredients:

14 ounces white chocolate, coarsely chopped[7]
½ cup heavy cream (35% cream)

1. Melt the white chocolate with the heavy cream. Whisk the mixture gently until smooth.
2. Let cool for 10 minutes and then pour over the chilled cake.[8] Using a long metal cake spatula, smooth out into an even layer.
3. Place the cake into the refrigerator for 30 minutes to set.

Assembling the Opéra Cake

(Note: The finished cake should be served slightly chilled. It can be kept in the refrigerator for up to 1 day).

Line a baking sheet with parchment or wax paper.

Working with one sheet of cake at a time, cut and trim each sheet so that you have two pieces (from each cake so you’ll have four pieces in total): one 10-inch (25-cm) square and one 10 x 5-inch (25 x 12½-cm) rectangle.

Step A (if using buttercream only and not making the ganache/mousse):

Place one square of cake on the baking sheet and moisten it gently with the flavoured syrup.

Spread about one-third of the buttercream over this layer.

Top with the two rectangular pieces of cake, placing them side by side to form a square. Moisten these pieces with the flavoured syrup.

Spread another third of the buttercream on the cake and then top with the third square of joconde. Use the remaining syrup to wet the joconde. Spread the remaining buttercream on top of the final layer of joconde and then refrigerate until very firm (at least half an hour).

Make the glaze and after it has cooled, pour/spread it over the top of the chilled cake. Refrigerate the cake again to set the glaze.

Serve the cake slightly chilled. This recipe will yield approximately 20 servings.

Step B (if making the ganache/mousse):
Place one square of cake on the baking sheet and moisten it gently with the flavoured syrup.

Spread about three-quarters of the buttercream over this layer.

Top with the two rectangular pieces of cake, placing them side by side to form a square. Moisten these pieces with the flavoured syrup.

Spread the remaining buttercream on the cake and then top with the third square of joconde. Use the remaining syrup to wet the joconde and then refrigerate until very firm (at least half an hour).

Prepare the ganache/mousse (if you haven’t already) and then spread it on the top of the last layer of the joconde. Refrigerate for at least two to three hours to give the ganache/mousse the opportunity to firm up.

Make the glaze and after it has cooled, pour/spread it over the top of the chilled cake. Refrigerate the cake again to set the glaze.

Serve the cake slightly chilled. This recipe will yield approximately 20 servings.