Opera Cake Recipe
Recipe: https://recipestripper.com/recipes/6d549f5d-eef0-4299-b20c-f4131ad19cab
Original source: https://bonnibakery.com/opera-cake/
Recipe image: https://bonnibakery.com/wp-content/uploads/2025/01/Opera-Cake_210-1.jpg

Classic French Opera Cake with seven layers of joconde sponge, coffee buttercream and chocolate ganache, finished with a shiny chocolate glaze.
Yield: 12
Prep time: PT145M
Cook time: PT15M
Total time: PT160M

Ingredients
- 160 ml Heavy Cream ((double cream))
- 130 g Dark Chocolate (chopped)
- 1 tbsp Unsalted Butter (15g (room temperature) )
- 6 Large Egg Whites ((keep yolks for the buttercream))
- 5 Large Eggs ((room temperature))
- 200 g Granulated Sugar ((caster sugar))
- 200 g Almond Flour ((ground almonds))
- 40 g Cake Flour
- 2 tbsp Unsalted Butter
- 100 g Granulated Sugar ((caster sugar))
- 120 ml Water
- 2 tbsp Espresso Powder
- 2 tbsp Amaretto ((optional) )
- 6 Large Egg Yolks ((room temperature - leftover from making the sponge))
- 150 g Granulated Sugar ((caster sugar))
- 60 ml Water
- 227 g Unsalted Butter ((cubed) )
- 1 tsp Vanilla Extract
- 1 ½ tbsp Espresso Powder
- ¼ tsp Salt
- 85 g Dark Chocolate
- 2 tsp Vegetable Oil
- 160 ml Heavy Cream ((double cream))
- 160 g Dark Chocolate ((chopped) )
- 1 tbsp Unsalted Butter ((room temperature))
- 1 tbsp Corn Syrup ((or liquid glucose) )

Instructions
1. [Make the Chocolate Ganache] Make the ganache first so it has time to cool while you make the other elements. Put the chopped chocolate in a medium bowl and put the heavy cream in a small saucepan over medium heat.
2. [Make the Chocolate Ganache] Heat the cream, stirring occasionally, until it is scalding hot. This means that there is steam rising from it and you can see tiny bubbles appearing on the surface. Don't let it boil.
3. [Make the Chocolate Ganache] Pour the hot cream over the chocolate and let it sit for 1-2 minutes, then stir in circles in the middle of the bowl until it comes together into a glossy ganache and all the chocolate has melted.
4. [Make the Chocolate Ganache] Stir in the room temperature butter until it has melted completely. Set the ganache aside to cool and thicken to a spreadable consistency.
5. [Joconde Sponge] Preheat the oven to 400°F / 200°C (180° fan-assisted). Line a half-sheet pan with a silicone baking mat or parchment paper and spray with baking spray. Divide the sugar by putting roughly 1/3 of it into a separate bowl.  Melt the butter in the microwave in a medium bowl and then set aside to cool while you make the batter.
6. [Joconde Sponge] Whip the egg whites on high speed in a stand mixer with the whisk attachment until they start to get frothy.
7. [Joconde Sponge] Take the smaller bowl of sugar and add it to the egg whites as they whip, one tablespoon at a time. Wait for about 15 seconds in between additions to give the sugar a chance to dissolve into the egg whites.
8. [Joconde Sponge] Once all the sugar has been added, keep whipping until a stiff meringue forms. It should be just before the stiff peaks stage, which means it will form firm peaks, but the top will still droop over slightly into a hook shape. Be careful not to overwhip the meringue.
9. [Joconde Sponge] Transfer the meringue to a separate bowl, then use the empty stand mixer bowl to combine the 5 whole eggs, almond flour, and remaining sugar. There is no need to clean your bowl in between.*
10. [Joconde Sponge] Whip together on high speed until it reaches the ribbon stage. This means that the mixture falls from your whisk in a steady stream and leaves a pattern on top of the batter for a few seconds before disappearing.
11. [Joconde Sponge] Scoop half of the meringue into the batter and fold it in gently with a rubber spatula until it is almost incorporated, but some pieces of white are still visible. Then add the remaining meringue and repeat, also only until almost incorporated.
12. [Joconde Sponge] Sift the flour on top of the batter and fold it in until completely incorporated. Make sure you get any flour from the bottom of the bowl.
13. [Joconde Sponge] Use your spatula to scoop a dollop of batter into the bowl of melted, cooled butter and mix it in thoroughly. This is called 'sacrificing' the batter, and it will help the butter to mix into the rest of the batter.
14. [Joconde Sponge] Add the sacrificed batter back into the main batter and gently fold it in with the spatula.
15. [Joconde Sponge] Pour the joconde batter into the prepared pan and gently spread it out to all the corners. Use your spatula or palette knife to get the batter as level and even as possible as it won't level out by itself in the oven.
16. [Joconde Sponge] Bake the sponge for 12-16 minutes or until it is starting to get a little color, is pulling away from the edges of the pan, and it springs back slightly when you press on it. Leave to cool completely before removing from the pan.
17. [Joconde Sponge] Once cooled, run a knife around the edges of the pan, then lay a large sheet of parchment paper on top of the sponge. Flip the pan upside down on the counter so that the sponge is sitting on top of the parchment paper. Peel away the mat or parchment paper that it was baked on.
18. [Make the Coffee Syrup] Take 1 tbsp of the water and mix it in a small bowl with the espresso powder until it dissolves. Set aside.
19. [Make the Coffee Syrup] Put the rest of the water in a small saucepan with the sugar over medium-high heat and bring to a boil until the sugar has dissolved and the liquid turns clear.
20. [Make the Coffee Syrup] Remove from the heat and add in the dissolved espresso and the amaretto (if you want to add it).  For a non-alcoholic version, just replace the alcohol with an equal amount of water.
21. [Make the Coffee Syrup] Leave the coffee soak to cool while you make the buttercream.
22. [Make the Coffee French Buttercream] Put the egg yolks into a clean stand mixer bowl and whip on medium-high speed until they are thick and very pale in color (about 5 minutes).
23. [Make the Coffee French Buttercream] In a small saucepan with a candy thermometer, make a sugar syrup by boiling the sugar and water over medium heat until it reaches exactly 240°F / 115°C.
24. [Make the Coffee French Buttercream] Immediately remove from the heat and, with the stand mixer on low speed, pour the hot syrup into the egg yolks in a very slow and steady stream. Try not to let the syrup hit the moving whisk as you pour.
25. [Make the Coffee French Buttercream] Turn the mixer up to high speed and whip until the mixture no longer feels warm, this may take about 10 minutes.
26. [Make the Coffee French Buttercream] Once the mixture has cooled enough that it doesn't feel warm to the touch, you can start adding your butter. With the mixer on high speed, add one chunk of butter at a time, letting each chunk incorporate before adding the next.
27. [Make the Coffee French Buttercream] Once all the butter is added, continue to whip on high speed for 1 minute. You should have a thick, glossy buttercream.
28. [Make the Coffee French Buttercream] Dissolve the espresso powder in a splash of hot water, then add it to the buttercream along with the vanilla and salt. Whip for 30 seconds everything is combined.For detailed tips, process pictures, and troubleshooting, see my French Buttercream post.
29. [Assemble the Opera Cake] Make sure you have all the elements ready and laid out in front of you. It's also best to have some kind of flat serving plate to work on so you can easily put the opera cake in and out of the fridge.
30. [Assemble the Opera Cake] Heat the dark chocolate in the microwave in 30-second increments until it is completely melted. Stir in the vegetable oil.
31. [Assemble the Opera Cake] Position the joconde sponge in front of you, and using a sharp knife, cut it into three even rectangles (see the process pictures in the post above for guidance).  For the most accurate results, I like to use a measuring tape to measure the whole length and divide by 3, to make sure I get three equal sizes.
32. [Assemble the Opera Cake] Set two of the rectangles aside on the parchment paper. Place the remaining rectangle on a separate piece of parchment paper, on the serving plate. Spread the melted chocolate on top of the joconde and smooth it out as evenly as possible. Don't worry about getting the edges perfect, as we are going to trim them later anyway. Put it in the fridge to set for 5-10 minutes, until it is completely hard.
33. [Assemble the Opera Cake] Once the chocolate is hard, flip the joconde sponge over so the chocolate side is on the bottom. Then use a skewer to poke holes all over the top - this will help the coffee syrup to soak into it, making it moist and filling it with flavor.
34. [Assemble the Opera Cake] Brush the coffee syrup all over the sponge with a pastry brush, then repeat once it has soaked in a little. Be generous with it, but don't oversaturate or it will go soggy.
35. [Assemble the Opera Cake] Put roughly half of the french buttercream on top of the sponge and spread it out as smoothly and evenly as possible. Crouch down to look at the cake at eye level to check for evenness - if the layers are not even, then the finished cake won't be either. Again, don't stress too much about the edges as they will be trimmed later.
36. [Assemble the Opera Cake] Put the next layer of joconde sponge on top and repeat the process with poking holes and soaking with syrup.
37. [Assemble the Opera Cake] Spread all of the ganache on top of this cake layer and smooth it out.
38. [Assemble the Opera Cake] Top with the final cake layer, poke holes and soak with coffee syrup.
39. [Assemble the Opera Cake] Spread the remaining French buttercream on top into a nice, smooth finish. Put the opera cake in the fridge to set for 30 minutes.
40. [Make the Glaze] After 30 minutes, check the cake by lightly touching the top of the buttercream, it should be set to the touch and not stick to your finger at all.
41. [Make the Glaze] Put the chopped chocolate, butter and corn syrup together in a bowl, then heat the heavy cream in a saucepan until scalding, just like we did for the ganache earlier.
42. [Make the Glaze] Pour the cream over the chocolate, butter, and corn syrup, let sit for 1 minute, then stir together until smooth and glossy.
43. [Make the Glaze] Take the opera cake out of the fridge and pour all of the glaze on top, spread it out to all four corners, then use your spatula to do one smooth swipe across the top. Put the opera cake back in the fridge to set for 10 minutes.
44. [Slice the Opera Cake] Lift the opera cake off of the serving plate using the parchment paper and set it down on your countertop.
45. [Slice the Opera Cake] Using a long, serrated knife, trim off the edges of the opera cake to leave nice, clean edges. The best way to do this is to warm your knife in hot water, wipe dry with a paper towel, then position it at the top of the cake, parallel with the work surface, and push straight down, keeping it level until it reaches the very bottom.Once you have cut through the bottom, slide the knife along the bottom to make sure it has cut cleanly. Wipe and re-warm your knife in between every slice to make sure you don't mess up those beautiful layers.
46. [Slice the Opera Cake] If you want to serve the opera cake whole, you can lift it and transfer it back onto the serving plate.To slice it, repeat the same process as for trimming the edges, cutting into individual slices.  You can then transfer those slices back onto the serving plate or serve them up individually.