Phew! This cake is probably the most ‘difficult’ recipe I have ever cooked. My style is not one of fine technical skill or finesse. So (deep breath), here’s what the opera cake consists of : the joconde (a thin cake made with ground nuts), which is brushed with syrup and followed by a layer of buttercream, then more joconde and syrup, more buttercream, more joconde and syrup, a layer of white chocolate mousse and finally (because that’s just not enough), a white chocolate glaze. A traditional opera cake contains darker chocolate and coffee flavours with an almond joconde, which I would love to try – as long as someone else makes it.
Here’s how I went wrong. The joconde, for some reason (I don’t know), refused to cook properly in the centre. I used the right size pans, the right oven temperature, the right method but it just started burning on top and stayed ultra-gooey in the centre. It was either my oven – very likely – or it was the type of nuts I used. Either way, I ended up removing the cakes from the tin, turning them over and re-baking them until they firmed up dammit! Eventually, it worked but that put me back about an hour what with all the deliberation over how to ‘sort it’, and I spent five or so hours making the entire cake. Next problem was the buttercream. I managed to make this the night before and everything was fine. When I came to re-beat it for use on the cake however, it had split. I read on the forum that, if this happens, the solution is to beat it and just keep going until you think the motor will blow on your mixer – eventually it will come back to a luscious buttercream and miraculously, it did!
Dramas over, the other components were pretty simple but I must admit, the whole thing was way too sweet for me. You need an occasion for a cake like this, a small slice is definitely enough.
Pistachio, Cointreau and Peppermint Opera Cake
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 (Note: If you do not have jelly-roll pans this size, do not fear! You can use different-sized jelly-roll pans like 10 x 15-inches.)
a few tablespoons of melted butter (in addition to what’s called for in the ingredients’ list) and a brush (to grease the pans)
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)
6 large egg whites, at room temperature
2 tbsp. (30 grams) granulated sugar
2 cups (225 grams) ground blanched pistachios
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 425F. (220C).
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 pistachios, 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 pistachio 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
½ cup (125 grams) water
65 grams granulated sugar
2ml peppermint extract
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
(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 hand held mixer
a bowl and a whisk attachment
1 cup (100 grams) granulated sugar
¼ cup (60 grams) water
seeds of one vanilla bean (split a vanilla bean down the middle and scrape out the seeds) or 1 tbsp. pure vanilla extract
zest of 2 oranges
1 large egg
1 large egg yolk
1¾ sticks (7 ounces; 200 grams) unsalted butter, at room temperature
2 tablespoons Cointreau
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 225F (107C) [*Note: Original recipe indicates a temperature of 255F (124C), however, when testing the recipe I found that this was too high so we heated to 225F and it worked fine] 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 the orange zest 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 below)
(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
7 ounces white chocolate
1 cup plus 3 tbsp. heavy cream (35% cream)
1 tbsp. Cointreau
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
14 ounces white chocolate, coarsely chopped
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. 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.
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.