Opera Cake from Parisian pâtisserie Dalloyau. Photos by Anita, Premium Member © Sarah Phillips Photos posted with permission.

It is hard to say exactly who invented the Opera Cake. But, the renowned Parisian pâtisserie Dalloyau popularized it as “L Opera”.’
The classic Opera Cake is defined as three thin layers of almond cake, also known as a joconde, a sponge cake, each soaked in a potent coffee syrup; a layer of espresso-flavored buttercream; one layer of bittersweet chocolate ganache; and a topping of chocolate glaze. Traditionally, the cake is decorated with the name “Opera” written in glaze across the top and finished with flecks or a piece of shimmering gold leaf, banned in some countries. The cake is cut into rectangular shapes and then served. It is a deceptive cake – at first glance, each servings looks at though it won't be overly filling, perhaps because of its multiple thin layers, but when you take one bite, the cake is rather rich, flavorful and delightful! This recipe is adapted from Dorie Greenspan, Paris Sweets. I added a lot more descriptive information and techniques to the recipe.
CAKE RECIPE HELP

Opera Cake interpretation at the famed Santa Barbara Biltmore Sunday Brunch, photo by Sarah Phillips © Sarah Phillips

STEP I: MAKE THE JOCONDE AND THE COFFEE SYRUP
NOTES: I like to prepare the cake a day in advance so the flavors blend together; make sure you keep it refrigerated. Greenspan recommends that the cake is best served slightly chilled, which I prefer, too.

JOCONDE (CAKE)
A JOCONDE is an almond sponge cake. This biscuit is named for the Mona Lisa (La Joconda in French). In addition to containing almonds, it differs from other sponge cakes by having whole eggs (rather than just yolks) beaten with sugar and ground almonds before the meringue, or beaten egg whites with sugar, is folded in. Joconde is baked in thin layers on baking sheets.

INGREDIENTS
Melted butter for sheet pans

6 large egg whites, at room temperature
2 tablespoons (30 grams) sugar
2 cups (225 grams) ground blanched almonds; measure almonds after being ground
2 1/4 cups (225 grams) powdered sugar, sifted
6 large eggs

1/2 cup (70 grams) unbleached all-purpose flour; spoon into measuring cup and level to rim
3 tablespoons (45 grams) unsalted butter, melted and cooled briefly

NOTES: This recipe makes a square Opera Cake that is impressive – 10 inches (25 cm) on a side. If this is more cake than you need, make the full cake, cut it into smaller size cakes and stock them in your freezer.

INSTRUCTIONS
1. Position the racks to divide the oven into thirds and preheat the oven to 425 degrees F (220 degrees C). Line two 12 1/2- x 15 1/2-inch (31-x-39-cm) jelly-roll pans with parchment paper and brush with melted butter.

2. Working in a clean dry mixer bowl fitted with the whisk attachment, beat egg whites on low speed until foamy. The bubbles in the egg white foam will become smaller and more even in size and foamy. When it reaches this stage, increase the mixer speed to medium-high. Then, add the sugar slowly in a steady stream at the side of the bowl.

After the sugar has been added, increase the mixer speed to high and beat until the peaks are stiff and glossy. If you do not have another mixer bowl, gently scrape the meringue (beaten egg whites and sugar) into another bowl.

3. In a mixer fitted with the paddle attachment, beat the almonds, confectioners' sugar and whole eggs on medium speed until light in color, fluffy and voluminous, about 3 minutes. Add the flour and beat on low speed only until it disappears.

4. With a large rubber spatula, gently scrape 1/3 of the meringue on top of the almond/flour mixture. mixture. Using a rubber spatula, gently fold together. Repeat two more times with the rest of the meringue.

5. Gently fold in the melted butter. The batter will deflate slightly.

6. Divide the batter between the pans and spread it evenly to cover the entire surface of each pan.

7. Bake the cakes for 5 to 7 minutes, or until they are lightly browned and just springy to the touch. Put the pans on a heatproof counter, cover each with a sheet of parchment paper, turn the cakes over and unmold. Carefully peel away the parchment, turn the parchment over and use it to cover the exposed sides of the cakes. Let the cakes cool between the parchment sheets.

STORAGE
The cakes can be made up to 1 day ahead, wrapped and kept at room temperature, or frozen for up to a month or more.

COFFEE SYRUP
INGREDIENTS
1/2 cup water
1/3 cup sugar
1 1/2 tablespoons (7 grams) instant espresso powder

INSTRUCTIONS
1. In a small heavy-bottomed saucepan, stir together the water, sugar and instant espresso powder, and bring to a boil. Stir occassionally to dissolve the sugar.

2. Remove from heat and let cool.

STORAGE
Use immediately or refrigerate indefinitely in a covered container until needed.

STEP II: MAKE THE COFFEE FRENCH BUTTERCREAM AND CHOCOLATE GANACHE
COFFEE FRENCH BUTTERCREAM / Recipe alone
INGREDIENTS
2 tablespoons (10 grams) instant espresso powder
2 tablespoons (15 grams) boiling water
1 cup (100 grams) sugar
1/4 cup (30 grams) water
1 large whole egg
1 large egg yolk
1 3/4 sticks (7 ounces; 200 grams) unsalted butter, at room temperature
1 teaspoon pure vanilla extract

INSTRUCTIONS
1. In a small bowl, dissolve the instant espresso with the boiling water; set aside.

2. Bring the sugar and water to a boil in a small heavy bottomed saucepan; stir just until the sugar dissolves. Continue to cook without stirring until the syrup reaches 255 degrees F (124 degrees C), as measured on a candy thermometer. Immediately remove the pan from the heat.

3. Meanwhile, put the egg and the yolk in the bowl of a mixer fitted with the whisk attachment and beat on high speed until the eggs are pale and foamy. When the sugar is at temperature, turn the mixer to low and slowly pour in the syrup, trying to avoid the beaters. When all of the syrup has been added, raise the speed to medium-high and continue to beat until the eggs are thick, satiny and room temperature, about 5 minutes.

4. Meanwhile, soften the butter with a fork in a mixing bowl until it is soft and creamy but not oily. With the mixer on medium speed, slowly and steadily add the butter in 2-tablespoon (30-gram) chunks. When all the butter has been added, raise the mixer speed to high and beat until the buttercream is thickened and satiny. Beat in the dissolved instant espresso powder and vanilla extract.

5. Transfer the mixture to a container; cover and refrigerate. Stir occasionally, until it is firm enough to be spread.

STORAGE
Icing must be kept refrigerated and will keep for about 1 week. Icing can be stored in an airtight container and frozen for up to 2 months.

CHOCOLATE GANACHE
INGREDIENTS
8 ounces (240 grams) bittersweet chocolate, finely chopped
1/2 cup (125 grams) whole milk
1/4 cup (30 grams) heavy cream
4 tablespoons (2 ounces; 60 grams) unsalted butter, at room temperature

INSTRUCTIONS
1. Place the chocolate in a medium heat proof bowl. Bring the cream to a boil in a small saucepan over medium heat. Boiling means the cream will actually rise up in the pan and threaten to boil over.

Immediately pour the boiling cream over the chopped chocolate. Tap the bowl on the counter to settle the chocolate into the cream, then let it sit for 1 minute until the chocolate softens. Using a rubber spatula, slowly stir in a circular motion, starting from the center of the bowl and working out to the sides. Be careful not to add too much air to the ganache. Stir until all the chocolate is melted, about 2 minutes. It may look done after 1 minute of stirring, but keep going to be sure it's emulsified or smooth.

2. Beat the butter with a fork in a mixing bowl until it is soft and creamy but not oily. Then, stir it into the ganache in 2 to 3 additions. Refrigerate the ganache, stirring every 5 minutes, until it thickens and is spreadable, about 20 minutes. You can also slowly stir the ganache set in an ice bath (water and ice).

STORAGE
The ganache can be packed airtight and refrigerated for up to 3 days or frozen for 1 month; bring to room temperature before using, which takes about a day.

STEP III: ASSEMBLE THE OPERA CAKE. MAKE THE CHOCOLATE GLAZE AND IMMEDIATELY GLAZE THE CAKE. SERVE
1. Line a baking sheet with parchment or wax paper. Working with one sheet of cake at a time, trim the cake so that you have two pieces: one 10-x-10-inches (25-x-25-cm) square and one 10-x-5-inches (25-x-12.5-cm) rectangle.

2. Place one square of cake on the parchment and moisten the layer with coffee syrup. Spread about three-quarters of the coffee buttercream evenly over the cake. (If the buttercream is soft, put the cake in the freezer for about 10 minutes before proceeding.)

3. Top with the two rectangular pieces of cake, placing them side by side to form a square; moisten with syrup. Spread the ganache over the surface, top with the last cake layer, moisten, then chill the cake in the freezer for about 10 minutes.

4. Cover the top of the cake with a thin layer of coffee buttercream. Smooth with an offset icing spatula. Refrigerate the cake for at least 1 hour or for up to 6 hours; it should be cold when you pour over the glaze. You can also rapidly chill it by placing it int the freezer for about 20 minutes.

Continue to the next step.

CHOCOLATE GLAZE
INGREDIENTS
5 ounces (150 grams) bittersweet or semi-sweet chocolate, finely chopped into 1/4-inch size pieces
1 stick (115 grams) unsalted butter

INSTRUCTIONS
1. Bring the butter to a boil in a small saucepan. Remove the pan from the heat and clarify the butter by spooning off the top foam and pouring the clear yellow butter into a small bowl; discard the milky residue. The butter can be clarified days in advance and stored on the countertop.

Melt the chocolate in the top of a double boiler, then stir in the clarified butter. Let cool to tepid.

IMMEDIATELY GLAZE THE CAKE:
1. Lift the chilled cake off the parchment-lined pan and place it on a rack over the parchment-lined pan.

2. Immediately, pour over the glaze, using a long offset spatula to help smooth it evenly across the top.

3. Slide the cake into the refrigerator to set the glaze and chill the cake.

SERVE
I like to serve the cake slightly chilled. At serving time, use a long thin knife, dipped in hot water and wiped dry, to carefully trim the sides of the cake so that the drips of glaze are removed and the layers revealed.

STORAGE
Each element of the cake can be made ahead, as can the assembled cake.

The assembled cake should be kept in the refrigerator, for 1 day, or you can freeze the cake, wrap it airtight once it is frozen, and keep it frozen for 1 month; defrost, still wrapped, overnight in the refrigerator.