Lavender & White Chocolate Opéra Cake - Daring Bakers May Challenge

Herewith I share with you my 10th Daring Bakers Challenge - Opéra Cake. Ta-da!

Do you know what that is? I didn't. I had to read up and look through Google images. I realised immediately this was something I had eaten at a glorious high tea at the Sofitel Wentworth a few months ago. According to Larousse Gastronomique "Opéra gateau is an elaborate almond sponge cake with a coffee and chocolate filling and icing." The founders of our wonderful Daring Bakers group, Lis & Ivonne set this months challenge with clear instructions to follow the recipe but adapt the flavourings to our likings as long as the overall appearance was light in colour.

I threw around many ideas for about a week and eventually decided on an old favourite flavouring, Lavender which I had mainly used for pannacottas (that reminds me, I don't think I've done them on BCM - I will soon!).

So Lavender and White Chocolate it was. I followed the recipe we were given to the letter, however I flavoured the soaking syrup with a few leaves of lavender, the white chocolate mousse with a few more leaves of lavender and several strategic drops of food colouring.

I hope you like the look of this - I worked very hard to complete this in one evening. It went down very well, but next time I share it around I will be cutting pieces half the size as it was incredibly rich! I enjoyed this recipe immensely. As I've said many times now, my confidence gets better every time I complete a challenge and this was no exception.

If you would like to see how my fellow Daring Bakers went, please head on over to the Daring Bakers Blogroll.

Here's what I did.

A Taste of Light: Opéra Cake

This recipe is based on Opéra Cake recipes in Dorie Greenspan's Paris Sweets and Tish Boyle and Timothy Moriarty's Chocolate Passion.


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
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) white sugar
2 cups (225 grams) ground blanched almonds
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

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

Preheat the oven to 425◦F. (220◦C).

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

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.

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.

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

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.

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.

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.

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 3 -5 cm piece of lavender leaves

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

Remove from the heat and let cool to room temperature.

For the buttercream

(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:

2 cups sugar
1/2 cup water
seeds of one vanilla bean
1 large egg
1 large egg yolk
1¾ cups unsalted butter, at room temperature
3 tablespoons of melted white chocolate

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

Continue to cook, without stirring, until the syrup reaches 225◦F (107◦C) [*Note: Original recipe indicates a temperature of 255◦F (124◦C), however, when testing the recipe I found that this was too high so we heated to 225◦F and it worked fine] on a candy or instant-read thermometer. Once it reaches that temperature, remove the syrup from the heat.

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.

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!

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).

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.

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.

At this point add in the white chocolate and beat for an additional minute or so.


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).

(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 (200g) white chocolate
1 cup plus 3 tbsp. heavy cream (35% cream)

Melt the white chocolate and the 3 tbsp. of heavy cream in a small saucepan.

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.

In the bowl of a stand mixer, whip the remaining 1 cup of heavy cream until soft peaks form.

Gently fold the whipped cream into the cooled chocolate to form a mousse. If it's too thin, refrigerate it for a bit until it's spreadable.

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 (400g) white chocolate, coarsely chopped
½ cup heavy cream (35% cream)
5 - 8 cm piece of lavender leaves

Melt the white chocolate with the heavy cream and the piece of lavender. Whisk the mixture gently until smooth.

Let cool for 10 minutes, remove the lavender and then pour over the chilled cake. Using a long metal cake spatula, smooth out into an even layer.

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.

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.


Sathya-rating ****