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–+ servings

Classic Opera Cake

Learn how to make the classic rich coffee chocolate cake from scratch. Enjoy the authentic taste with the incredible aroma!
Author ayacaliva
Total Time 5 hours
Course a whole cake, cake, Chocolate cake, classics
Servings 10 slices
4.75 from 4 votes
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Equipment

  • Stand mixer or hand mixer
  • Spatula
  • Small saucepan
  • Sieve
  • Baking sheet pans
  • Pastry brush
  • Knife
  • Large knife

Ingredients

Biscuit Joconde

  • 3.5 oz Powdered Sugar
  • 3.5 oz Almond flour
  • 5.3 oz Whole eggs about 3 eggs
  • 4.9 oz Egg white from about 4 large eggs
  • 2.47 oz Granulated sugar
  • 1.2 oz All-purpose flour
  • 0.5 oz Butter

Coffee Syrup

  • 1.2 oz Ground coffee
  • 12 oz Water
  • 2.47 oz Granulated sugar
  • 3.5 oz Cognac

Chocolate for Sponge Cake

  • 1.2 oz Dark chocolate
  • 0.25 oz Oil

Coffee Buttercream

  • 5.3 oz Milk
  • 0.7 oz Ground coffee
  • 2.47 oz Granulated sugar
  • 2.47 oz Egg yolks from about 4 large eggs
  • 8 oz Butter 2 US sticks

Chocolate Ganache

  • 10.6 oz Dark chocolate I used 58% couverture chocolate.
  • 10.6 oz Heavy cream

Chocolate Glaze

  • 5.3 oz Dark chocolate I used 58% couverture chocolate.
  • 1 oz Oil

Chocolate to draw on top (Optional)

  • Some Dark chocolate (optional) or use the extra chocolate glaze

Instructions
 

  • Biscuit Joconde
    1. Make one batch of my biscuit Joconde recipe. Follow the steps in the post to make it successful. Pour the batter into 2 rectangle sheet pans. (10.5 inches | 26.7 cm ✖︎ 15 inches | 38 cm.) You can also use one full-size sheet pan or 4 quarter sheet pans. Bake at 410ºF (210ºC) for 6 - 7 minutes until the surface looks golden brown. 
    2. Take them out from the sheet pans and let them cool on a cooling rack. Cut each in half to make 4 layers of sponge cake. Set them aside.
    Tips💡
    1. Spread the sponge cake batter very thinly: The thin layers create a more delicate, amazing texture - Don’t worry, even if it might look super thin!
    2. When you use 2 racks for 2 trays in an oven, switch the position toward the end to bake them evenly. Or use one rack if they fit in and rotate them toward the end if necessary.
    3.5 oz Powdered Sugar, 3.5 oz Almond flour, 5.3 oz Whole eggs, 4.9 oz Egg white, 2.47 oz Granulated sugar, 1.2 oz All-purpose flour, 0.5 oz Butter
    spreading the batter of biscuit joconde in a sheet pan
  • Spread melted chocolate on the bottom layer.
    1. Mix melted chocolate and oil and spread it thinly over the baked side of one of the sponge layers. 
    2. Chill it in the fridge until it's set. Cut a cake board into the cake size and place the sponge cake layer on the top (chocolate side facing down). The board helps to move the cake easily, especially when pouring the chocolate glaze on top at the very end.
    Tip💡
    Why do you need to coat the chocolate? - The chocolate layer creates a barrier on the bottom and helps to transfer the cake a lot more easily when serving it.
    1.2 oz Dark chocolate, 0.25 oz Oil
    spreading a thin layer of chocolate on a biscuit joconde sponge
  • Coffee Syrup
    1. Heat water and sugar in a small saucepan until it starts simmering.
    2. Remove from the heat and add ground coffee. Mix and place a lid on top to let it steam for 10 – 15 minutes.
    3. Strain it and discard the ground coffee. 
    4. Add cognac and mix.
    Tips💡
    1. Do not boil the coffee syrup for a long time to avoid the liquids from evaporating too much.
    2. Yes, it is a VERY generous amount of cognac! But surprisingly, it works so well. I rarely add this much alcohol to my desserts, but it plays a sub-main role in an opera cake.
    1.2 oz Ground coffee, 12 oz Water, 2.47 oz Granulated sugar, 3.5 oz Cognac
    adding cognac in coffee syrup
  • Coffee Buttercream
    1. Heat the milk in a small saucepan until it starts simmering. 
    2. Stop the heat and add ground coffee. Place a lid and let it steam for 10 - 15 minutes, just like how we did with the coffee syrup.
    3. Meanwhile, mix egg yolks and sugar in a bowl until it looks pale in color.
    4. Pour the strained coffee liquid into the yolk mixture as you mix.  
    5. Pour it back into a saucepan and continue heating it gently at low heat until it starts getting thickened a bit.
    6. Strain it in a bowl and let it cool to room temperature.
    7. Whip soft butter until it gets very fluffy.
    8. Add about ⅓ of the coffee sauce and whip. Add the rest of the sauce and continue whipping it until it looks fluffy.
    Tips💡
    1. Boiling milk overfloat quickly! Pay close attention to the pan while heating it.
    2. Heat the coffee sauce VERY gently, especially toward the end, to prevent yolks from getting cooked. 
    3. It is important to use soft butter to make the buttercream smooth and fluffy. And whipping it a lot makes a big difference! The whipped buttercream feels lighter in your mouth because of the air inside. 
    4. The coffee coffee sauce is hot right after it's made. Cool it to room temperature before adding butter to prevent it from melting. Do not chill the sauce to prevent the butter from getting separated once they are combined.
    5.3 oz Milk, 0.7 oz Ground coffee, 2.47 oz Granulated sugar, 2.47 oz Egg yolks, 8 oz Butter
    whipping mocha buttercream
  • Chocolate Ganache
    1. Melt the chocolate. Heat the heavy cream until it feels slightly warm so it blends more easily.
    2. Add ¼ of heavy cream and mix until smooth. 
    3. Once it looks even, repeat the process until you add all the heavy cream. I divided it into 4 times this time.
    Tip💡
    Depending on the temperatures of chocolate and heavy cream, the ganache might be too soft to spread on a sponge cake right after it's made. In that case, wait some time - it’ll soon get firmer as it cools down. 
    10.6 oz Dark chocolate, 10.6 oz Heavy cream
    finished dark chocolate ganache in a bowl
  • Assemble the cake.
    This cake is made with 4 layers of Joconde sponge cake soaked in coffee syrup, 2 layers of chocolate ganache, and 2 layers of coffee buttercream.
    Follow the 8 steps:
    1. Apply ¼ of the coffee syrup on the first sponge layer with a pastry brush.
    2. Spread half of the chocolate ganache with an offset spatula.
    3. Place the 2nd sponge cake on top (the baked side facing down) and apply the coffee syrup.
    4. Spread half of the coffee buttercream.
    5. Place the 3rd sponge cake and apply the coffee syrup.
    6. Spread the remaining ganache.
    7. Place the 4th sponge cake layer and apply the remaining coffee syrup.
    8. Spread the rest of the buttercream.
    Chill the cake in the fridge.
    Chill it in the fridge after assembling it until the ganache and buttercream are set completely for at least one hour.
    I recommend waiting overnight if you have time so the coffee syrup spreads more evenly throughout the sponge cake. Wrap the surface with plastic wrap when chilling it overnight.
    Tips💡
    1. You might feel shocked to see the amount of coffee syrup, but it works so well for this cake! Don’t be afraid of using it all. When you see syrup floating on the sponge's surface, make shallow cuts with a knife all over the sponge cake evenly. The syrup goes in deeper immediately. 
    2. The baked side of the sponge cake doesn’t soak the syrup well. The lighter side can soak up a lot more! Face the baked side down when assembling the cake.
    3. If the ganache gets too firm to spread while you are assembling the cake, heat it slightly to make it softer again.
    4. Spread each layer very thinly. Thin layers create a delicate texture that makes this cake exceptional. It's surprising to taste how much difference only the thickness makes! I recommend using a piping bag with a flat pastry tip to spread the buttercream more easily.
    piping mocha buttercream on top of biscuit sponge to assemble a opera cake
  • Chocolate Glaze
    Preparation: Set a wire rack on a baking sheet pan with plastic wrap on top. We are placing the cake on the rack and pour the glaze.
    1. Melt the chocolate and add oil. Mix gently to prevent it from containing a lot of air bubbles. 
    2. Pour it on a cake right away when it feels slightly warm. The cake should be removed from the fridge right before pouring it.
    3. Immediately spread it thinly with an offset spatula, moving it back and forth a few times. Check out the video tutorial to see the movement. Do it quickly before the chocolate starts getting hard. 
    4. As an option, draw "Opera cake" on top of the cake with melted chocolate or the extra chocolate glaze that fell on a sheet tray. 
    Tips💡
    1. The combinations of the temperatures are important. For example, when the cake is freezing cold, you need a warmer chocolate glaze.
    2. You can also use my chocolate mirror glaze recipe for a shinier, darker glaze. It's more tolerant to the temperature gap.
    5.3 oz Dark chocolate, 1 oz Oil, Some Dark chocolate (optional)
    coating chocolate on top of a opera cake
  • Slice the cake.
    1. Dip a sharp knife in the hot water. (or heat a knife with a torch)
    2. Wipe it with a towel or paper.
    3. Hold it straight and slide it down. 
    4. Pull it off when it goes all the way down. 
    5. Wipe a knife and repeat the process.
    You can slice it into rectangles, squares... any shapes and sizes you like!
    Now, enjoy!!! Bon-Appetit. ☕️ 
    I recommend leaving the cake for about 10 minutes or more at room temperature after slicing it. The chocolate ganache and coffee cream get softer and melt more in your mouth.
    a cut side of a opera cake

Video

Notes

How to store it:

Store in an airtight container for up to 5 days in the fridge. I recommend eating it within 1 - 2 days for the best taste!

Nutrition

Calories: 816kcal | Carbohydrates: 63g | Protein: 12g | Fat: 65g | Saturated Fat: 35g | Polyunsaturated Fat: 3g | Monounsaturated Fat: 19g | Trans Fat: 1g | Cholesterol: 219mg | Sodium: 69mg | Potassium: 112mg | Fiber: 6g | Sugar: 41g | Vitamin A: 1249IU | Vitamin C: 0.2mg | Calcium: 85mg | Iron: 1mg
Tried this recipe?Let us know how it was!