White Opéra Cake with Lemon Butter Cream, White Chocolate Mousse & Almonds

White Opéra Cake

Sometime last year while browsing some food blogs I came across The Daring Bakers. Like some secret cult their website is closed to non-members and after some digging for info (to no avail) I decided to join them. The curious kid in me just had to know what they were all about and I sorely hoped that the initiation process won’t be too painful.

After joining, I finally found out the truth. One recipe a month is decided upon and is then baked by all members. All members’ creations are then revealed on a decided date. Fair enough, I thought, pulling up my sleeves, it surely can’t be difficult; the “Daring” word in the group’s name is probably just to flatter themselves.

How wrong I was. Completely underestimating the first recipe, which was one of Dorie Greenspan’s cakes, came out as a total flop. Hmpf. I still don’t know what went wrong, but it popped my confidence balloon, which now lay on the floor resembling a shrivelled condom.

The following month’s challenge I decided to give a miss. Frozen cheesecake lollipops, what?!?! After seeing the beautiful, artsy decorations the bloggers came up with I was green with envy. I really should have tried making them. Hmpf. I told myself that next time I was going to kick some ass.

On the first of May I eagerly checked out the next recipe. After making up new swear words I was seriously contemplating running away from the mess I got myself into. A cake with 5 elements? Why can’t it just be sponge and butter cream? It’s all going to end up in gooey-masticated mess in people’s stomach anyway. Plus, I’m on a diet; I can’t afford to eat such luxuriously creamy things.

After a few days I decided to give it a whirl. The reason I joined this group was to learn to bake and this was the ideal opportunity to practise. Then the baking began…

**** This is the scary part, people. Don’t stop reading now. You have to truly appreciate the length of the recipe and see what I had to go through! ****

White Opéra Cake with Lemon Butter Cream, White Chocolate Mousse & Almonds
Serves plenty of people
Preparation: hours and hours – Cooking: lost count

White Opéra Cake

For the Joconde
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)
  • 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)
  • 6 large egg whites, at room temperature
  • 2 tbsp. (30 grams) granulated sugar
  • 2 cups (225 grams) ground blanched almonds (Note: If you do not want to use almond meal, you can use another nut meal like hazelnut. You can buy almond meal in bulk food stores or health food stores, or you can make it at home by grinding almonds in the food processor with a tablespoon or two of the flour that you would use in the cake. The reason you need the flour is to prevent the almonds from turning oily or pasty in the processor. You will need about 2 cups of blanched almonds to create enough almond meal for this cake.)
  • 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.
    Preheat the oven to 425◦F. (220◦C).
  2. Line two 12½ x 15½- inch (31 x 39-cm) jelly-roll pans with parchment paper and brush with melted butter.
  3. 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.
  4. 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.
  5. Add the flour and beat on low speed until the flour is just combined (be very careful not to overmix here!!!).
  6. 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.
  7. 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.
  8. 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.
  • The joconde can be made up to 1 day in advance and kept wrapped at room temperature.

With all the warnings in brackets next to the steps, I was pretty paranoid. What if I overdid it with the stirring? What if this is a flop again? Argh. Since I’ve never folded in my life, the mixture ended up with blotches of white in it, which were the whisked egg whites. After ages of folding slowly I was scared that I was going to push all the air out of the light mixture and end up with two heavy bricks, so I stopped before the egg was properly mixed in and stuffed the concoction in the oven anyway. As I was waiting for the sponge to rise I started debating with myself whether I should have folded further. When I realised there was nothing else I could do, I started praying to the baking gods that the sponge will come out okay. They already played a cruel little joke on me the first time round. Amazingly, when I dared to peek in the oven a few minutes later, the sponges looked normal, you know, the way they should, without any white blotches. It seemed like the gods listened to my pep talk and decided to toy with other bakers instead. Great! Now on to the syrup.

For the Syrup
What you’ll need
  • a small saucepan
  • ½ cup (125 grams) water
  • 1/3 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.
  • The syrup can be made up to 1 week in advance and kept covered in the refrigerator.

Hmmmm. The syrup doesn’t have the consistency of syrup; more like sweet brown water with a hint of bitterness from the vanilla. Whatever, it’s good enough for jazz.

For the Butter Cream
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
  • 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 (Note: If you are flavouring your buttercream and do not want to use the vanilla, you do not have to. Vanilla will often enhance other flavours but if you want an intense, one-flavoured buttercream, then by all means leave it out!)
  • 1 large egg
  • 1 large egg yolk
  • 1¾ sticks (7 ounces; 200 grams) unsalted butter, at room temperature
  • 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) [*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.
  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).
  • 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.

There was an alternative to the butter cream listed, which I made instead, but it was rubbish. I didn’t wait long enough for the sugar to melt and instead ended up with crunchy sugar that boiled and ended up forming hard clumps that sploshed like stones into the egg mixture. Needless to say it was a crunchy butter cream; no mater how long I let the mixer go at it. I decided against using it in my cake and luckily had enough unsalted butter left to make a new batch, but made it differently this time. Added more butter than the recipe stated though. Right, let’s carry on.

For the White Chocolate Mousse
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. liqueur 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.
  • The mousse can be made ahead and refrigerated until you’re ready to use it.

White chocolate isn’t as easy to melt as dark chocolate. I waited ages for the pieces to melt and a few minutes later I sat with a coagulated white mass with yellow oil drifting on top. It was time for a little intervention. The oil was drained from the glass bowl and more cream added and slowly but surely it all blended in one sweet, smooth sauce. Just perfect. The rest was easy peasy.

By this time it was 8 hours since I started making this cake when I started to assemble it. Yikes, I trimmed too much off the edges of the sponge, but it was still a very reasonable sized cake. Afterwards I put it in the fridge and added the glaze the following day.

For the Glaze
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.
  • It’s best to make the glaze right when you’re ready to finish the cake.
Assembling the Opéra Cake
  1. Line a baking sheet with parchment or wax paper.
  2. 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.
  3. Place one square of cake on the baking sheet and moisten it gently with the flavoured syrup.
  4. Spread about three-quarters of the buttercream over this layer.
  5. Top with the two rectangular pieces of cake, placing them side by side to form a square. Moisten these pieces with the flavoured syrup.
  6. 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).
  7. 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.
  8. 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.
  9. Serve the cake slightly chilled. This recipe will yield approximately 20 servings.
  • The finished cake should be served slightly chilled. It can be kept in the refrigerator for up to 1 day

Yet again the white chocolate separated from its “oil” and the cream saved it again. Weird stuff. Poured on the glaze, sprinkled it with slivered almonds and chilled it.

There was so much cake; I had to take some to the neighbours, which suddenly made me very popular. It tasted quite good as far as cakes go, but if you wonder if I’ll ever make it again the answer is hell no! The kitchen was a disaster area afterwards and it took a few days to clean up bit by bit.

I’m proud to say I’ve completed my first ever baking challenge with great success. Very DARING indeed!

P.S. Tired after reading this? Why not try this simple cake, with almond and coconut cream, from Coffee & Vanilla instead?

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  1. says

    Wow, for all you went thru, it still looks great! Good for you for not giving up! I joined the same month you did and I actually have made the Party cake 2 times! I loved that one. I probably won’t make the “light” opera cake again, but I would be interested in the traditional one!

  2. says

    Good for you for sticking with it and getting it done. The lemon sounds like it was delicious. When I first glanced at that recipe, I swear I broke out in a cold sweat!

  3. says

    That’s lovely! And yes, I do appreciate the work that went into it…I tried twice and neither came out. Congrats on a successful Ninja Baker challenge.

  4. says

    This definitely would have blown my brain to bits had I not made the components on separate days; I hate doing mass amounts of dished, which I save for holidays. I commend you for making it all in the same day. It wasn’t a marathon baking day, it was more like an ultramarathon!

    Great job and welcome to the Daring Bakers!

    P.S. What will you do if your neighbors request this cake? 😀

  5. says

    Great post and challenge, glad you stuck it out as your cake turned out absolutely gorgeous! I’m glad I was’nt the only one thinking about egg-white folding during baking.

  6. says

    Great job on using the white chocolate! I’ve encountered a few DBers who had problems with the fickle white choc. You guys are all making me wish I didn’t have to miss this challenge!

  7. says


    I love the review – makes me laugh! As for your verdict of not repeating this – the picture looks good enough to fall into the “trap” again in my opinion.

    Good for you for making it through!


  8. says

    Good job! I totally chickened out on the french bread challenge – probably would have found the time if had involved buttercream though…

  9. says

    You did a great job on your cake. I’m delighted that you gave this month’s challenge a try. It’s interesting, this was my 9th challenge and each recipe has given me a chance to stretch my skills in the kitchen. Not to mention learn some new ones in the process of making the recipes. Even the ones that don’t turn out the best are real learning experiences. A belated welcome to the Daring Bakers.

    Natalie @ Gluten A Go Go

  10. says

    Michelle – I can see that you and I think alot alike. You did a great job – scary as it was – it’s such a high (and doubly so if you tasted the cake) to finish this challenge.

  11. says

    It’s recipes like this that make me tell people that I’m not a baker!! [breathes into brown paper bag to stop hyperventilating in panic] I am in awa of you and the other Daring Bakers for even attampting this, and just look at how glorious your result is! I wish I lived closer 😉

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