Gâteau Opéra or French opera cake is the French answer to an Italian tiramisu. It is a classic of elegant French patisserie. It consists of an almond sponge cake soaked in coffee syrup, coffee buttercream, and chocolate ganache layered into a seven-layer dish. Traditionally, the decadent cake slices are cut into small rectangles, and decorated with the word “opéra,” but I opted for a treble clef instead. The inventor of this elegant cake, the French Cyriaque Gavillon aimed to provide the whole experience in one small bite. Once his wife tried his concoction, she claimed that this cake reminded her of the Parisian opera house Palais Garnier. Voilá the French opera cake was born. The pastry shop Dalloyau where Gavillon was employed, has been serving this cake since 1955. This is as French as it gets. But I will warn you, it does have many components and takes its amount of time to prepare. But slices can be frozen and components made in advance. You will be rewarded with the most delicious cake that so nicely combines the coffee and chocolate flavor. Maybe you will give this a try?
It took me, an experienced baker with a KitchenAid, about an hour to prepare all components. Assembling the cake probably took as long with all the chilling involved. But as mentioned before, it does have many components, which all require a bit of time. The good thing though is that you can make a lot in advance. Take your time and be patient, I am sure you will be rewarded. Even if you have some mistakes here and there, I am sure it will taste great. When I was doing reasearch in the Internet, I finally decided to use this recipe. However, there are two things I altered. First I made real coffee syrup instead of using instant coffe. I feel the flavor is so much better this way. Second, instead of making Italian buttercream, which requires you to boil sugar to a certain temperature, which you then need to add in a stream to beaten eggs, I decided to go the Swiss route. I found it important to provide a recipe that anyone can do, even if you don’t have a thermometer. Feeling with your fingers whether sugar has dissolved is easier in my opinion than guessing the temperature of boiling sugar. I was inspired by this recipe.
Credit: Adapted from patissland (in French)
Gâteau Opéra, or French opera cake consists of an almond sponge cake that is brushed with coffee syrup, a coffee buttercream, and chocolate ganache. It has seven layers and is usually served in rectangles. For the coffee syrup combine the ingredients in a small pot and bring to a boil. Simmer until it has reduced to about half and has a glossy kind of consistency, similar to syrup. It took me 10 minutes. Set aside. For the coffee buttercream heat the eggs in a waterbath while stirring until they reach 71 degrees Celsius. This takes a few minutes. If you don't have a thermometer, rub a bit between your fingers, if you cannot feel the sugar anymore, you are good to go. Beat until cold and almost white in color, this will take about 10 minutes. Then add the butter by the spoonful. If your buttercream looks soupy, you need to chill it in the freezer or fridge before continuing. If it looks curdled, take a few spoons and briefly heat in the microwave or stovetop, then put back with the rest. Your final buttercream should look glossy and smooth. Add about 3 tablespoons of the coffee syrup and the vanilla extract, beat for another minute until combined. Add about 3-4 tablespoons of water to the coffee syrup. You can also add a coffee liquor such as Kaluha instead of water. For the ganache bring heavy cream to a boil, then add chocolate in chunks. Stir until you have a homogeneous mix. Immediately transfer to fridge to cool and harden. For the almond sponge line a baking sheet of 30x40 cm (standard size in Germany) with parchment paper. Preheat oven to 180 degrees Celsius. Now first weigh and prepare all ingredients before continuing. Melt the butter, weigh almonds and flour into a small bowl. Give 100 grams of the icing sugar to the eggs in a large bowl, weigh 50 grams of the icing sugar into a small bowl. Separate the egg whites also into a small bowl. Keep a sieve and spatula close. First beat the egg whites with a pinch of salt with a handmixer. Once foamy, add the sugar. Beat on high until you have stiff peaks, this will need a few minutes. Without cleaning the mixer, beat the full eggs and sugar until lighter in color and thicker in consistency. Sieve the almonds and flour on top and add the cooled-off butter. Only mix on low until combined. Now add the meringue in three steps, use the spatula and try not to deflate. Gently fold until combined and immediately pour into prepared baking pan. Be sure to spread evenly to the rim. Bake for 10-12 minutes on medium rack. Once done, immediately turn upside down so that the parchment paper is facing you. Quickly spray with a bit of water and peel off parchment paper, this is best done while still warm, then let cool. Once cool, divide with two cuts, you want to get two squares of 20x20cm (they are side by side) and two of 10x20cm. Best is to use a ruler. You will have four pieces at the end, two the same size, and two combined having the same size as the others. The order when assembling is as follows: sponge, coffee syrup, buttercream, ganache, sponge, coffee syrup, butter cream, sponge placed upside down and ganache. In more detail I did it as follows: First I put everything inside of a brownie cake pan lined with parchment paper. Then I used one of the "full" sponge cake layers of 20x20cm, this I brushed with coffee syrup and spread half of the buttercream on top and about half of the ganache. I then chilled this for 15min. Then I put the two 10x20cm sponge cakes to make one square on top, brushed it with coffee syrup and spread the second half of the buttercream. The third sponge cake I first brushed with coffee syrup and then placed it upside down (soaked side down) on the buttercream. On top of everything I spread the remaining ganache, but I kept a little in order to write the treble clef later on, you don't need much for that. I chilled the cake prepared like this overnight. Once ready, lift cake using the parchment paper and trim all sides so that the layers become visible. I used a large serrated knife. My square had 17.5cm on each side. I then measured with a ruler and cut the square in half vertically, horizontally I cut it in four equal pieces so that I had 8 rectangular pieces in the end. For clean cuts, be sure to clean knife after every cut. If desired, reheat the left ganach and using a piping bag with a small tip, write the word "opera" or paint a treble clef like me. If you have none left, you may also heat a bit of chocolate to achieve the same. It also works plain. Each piece can be frozen if kept airtight. Chilled, the cake will keep for about four days.Gâteau Opéra, French Opera Cake
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