Opera Cake

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Prep 2hr (+ cooling time)Bake 8-10minMakes 18 serves

Created by Make Me a Baker student, Karthika Biju for her graduation, this stunning cake brings together numerous techniques learnt throughout the 6-month course. A real challenge, this dessert is an exquisite combination of chocolate and coffee-infused layers of almond sponge, ganache, chocolate croustillant, hazelnut praline and Swiss meringue buttercream. Karthika finished each portion of cake with gold dust and leaf and also personalised them with a chocolate disc monogramed with her initials. Not for the faint-hearted baker, this recipe is nothing short of a challenge but the results will definitely reflect the effort.


Edible gold leaf and dust, to decorate

    Joconde (Almond Sponge)

    Melted butter, to grease
    5 eggs, at room temperature
    140g almond meal
    140g soft icing sugar mixture
    30g plain flour
    5 egg whites
    30g caster sugar
    ¼ teaspoon salt
    30g unsalted butter, melted

      Coffee Syrup

      160ml (2/3 cup) water
      100g caster sugar
      3 teaspoons instant coffee powder

        Hazelnut Praline Paste

        125g whole raw hazelnuts
        75g caster white sugar
        2 teaspoons water
        ¼ teaspoon salt

          Chocolate Croustillant

          40g good-quality dark chocolate (45% cocoa), chopped or callets
          30g Hazelnut Praline Paste
          70g Paillette Feuilletine (see Baker’s Tips)

            Chocolate Ganache

            160g good-quality dark chocolate (45% cocoa), chopped or callets
            160ml (2/3 cup) thickened cream

              Swiss Meringue Coffee Buttercream

              4 egg whites, at room temperature
              200g caster sugar
              1/2 teaspoon salt
              250g unsalted butter, at room temperature
              Coffee extract, to taste

                Chocolate Glaze

                6.6g gelatine leaves 
                250ml (1 cup) chilled water
                125ml  (1/2 cup) room temperature water
                225g caster sugar
                150g good-quality dark chocolate (70% cocoa), callets or chopped
                30g cocoa powder, sifted
                65ml pure cream (35% butterfat)

                  Monogramed Chocolate Discs

                  70g good-quality dark chocolate (45% cocoa), callets or chopped
                  Edible gold lustre paint (See Baker’s Tips)
                  Wax seal (kept in freezer for at least 45 minutes)

                        Joconde (Almond Sponge Cake)

                        1. To make the Joconde, preheat the oven to 200°C (180°C fan-forced). Brush two 23cm x 33cm shallow baking trays with melted butter and line the base and sides of each with one piece of non-stick baking paper, cutting into the corners to fit.
                        2. Sift the almond meal and icing sugar into a large bowl. Add the whole 5 eggs and use an electric hand mixer to mix until the mixture is creamy. Stir in the flour until just combined.
                        3. Use an electric mixer with a whisk attachment on medium speed to whisk the egg whites and salt in a large clean bowl until soft peaks form. Gradually whisk in the sugar and continue to whisk until stiff peaks form. Use a spatula or large metal spoon to fold the egg whites through the almond mixture. Add the melted butter and fold gently together.
                        4. Divide the batter evenly between the prepared tins. Bake in preheated oven for 8-10 minutes until lightly golden and cooked through. Cool in the tins.
                        5. Carefully turn the cooled cakes onto a cutting board and cut each into one 20cm square and one 10cm x 20cm rectangle.

                        Coffee Syrup

                        1. To make the Coffee Syrup, place the water, sugar and coffee into a small saucepan and stir over medium heat until the sugar dissolves. Bring to the boil then remove from heat and set aside to cool completely.


                        1. Place the sugar and water in a saucepan over low heat. Leave it to heat until the sugar has melted. Do not stir. Continue cooking until it has turned a golden caramel.
                        2. Meanwhile, fill your sink with cold water. Once the caramel is ready, dip the base of the saucepan in the cold water for a few seconds to stop the cooking process. Set the pan on a towel on the bench.

                        Hazelnut Praline Paste

                        1. To Make the Hazelnut Praline Paste, reduce the oven temperature to 180°C  (160°C fan-forced) and roast the hazelnuts for 10-15 minutes, stirring them every 5 minutes, or until aromatic and the skins start to crackle.
                        2. Wrap the warm hazelnuts in a tea towel and set aside to steam for 10 minutes. Use the tea towel to rub to hazelnuts against it and each other to remove the skins.
                        3. Line an oven tray with non-stick baking paper or a silicone mat. Place the sugar and water in a small heavy-based saucepan and stir over medium heat until the sugar dissolves. Bring to a simmer and simmer over medium heat, brushing down the sides of the saucepan with a pastry brush dipped in water to remove any sugar crystals from the sides of the pan, until a deep golden toffee forms. Remove from the heat add the toasted skinned hazelnuts but don’t stir. Pour immediately onto the lined tray and set aside to cool completely.
                        4. When the toffee is cool, break into small pieces. Add about a quarter of the toffee shards to a food processor bowl and process until ground. With the motor running, add the remining toffee shards and process until ground. Add the salt and continue to process until a smooth paste with a peanut butter consistency forms (see Baker’s Tips).

                        Chocolate Hazelnut Croustillant

                        1. To make the Chocolate Croustillant, place the chocolate in a heatproof bowl and place over a saucepan of barely simmering water (don’t let the base of the bowl touch the water). Stir occasionally until melted and smooth.
                        2. Add Pailleté Feuilletine and Hazelnut Praline Paste to the melted chocolate and stir to combine. Spread the croustillant over the 20cm square layer of sponge cake on the board. Place in the fridge to set

                        Chocolate Ganache

                        1. To make the Chocolate Ganache, place the chocolate in a heatproof bowl. Heat cream in a small saucepan over medium heat and bring just to the boil.
                        2. Pour the cream over the chocolate and set aside for 1 minute. Stir until smooth. Set aside to cool at room temperature, stirring occasionally, until it thickens to a peanut butter consistency (see Baker’s Tips).

                        Coffee Buttercream

                        1. To make the Coffee Buttercream, combine the egg whites, sugar and salt in a medium heatproof bowl. Place the bowl over a pan of simmering water (don’t let the base of the bowl touch the water). Use a balloon whisk to stir until the sugar dissolves. Continue to stir until the mixture reaches 70°C on a thermometer.
                        2. Transfer the mixture to the bowl of a stand mixer and whisk on high speed with the whisk attachment until the mixture is very thick and glossy and has cooled completely to room temperature.
                        3. Replace the whisk with the paddle attachment and gradually add the room temperature butter a tablespoon at a time, beating well on medium-high speed after each addition, before adding the next lot. Once all the butter has been incorporated, beat in the coffee extract.

                        Cake Assembly

                        1. Remove the croustillant-coated sponge cake layer from the fridge and carefully flip it onto a on a another cutting board with chocolate croustillant facing down. Brush the sponge with about a third of the coffee syrup and then spread with half of the coffee buttercream. Place the two 10cm x 20cm sponge layers side by side on top to cover and brush with half of the remaining coffee syrup.
                        2. Reserve about 1/4 cup of the ganache and spread the sponge evenly with the remaining chocolate ganache. Top with the remaining layer of sponge cake and brush well with the remining coffee syrup. Spread with the remaining buttercream to cover and even the surface using an offset spatula or cake scraper. Cover and refrigerate the cake for at least 2 hours or overnight.

                        Monogramed Chocolate Discs

                        1. Line a tray with non-stick baking paper. Remove the wax seal from the freezer and place in a bowl of ice.
                        2. Melt the chocolate in the microwave for 10 seconds bursts on high, stirring well after each burst until the chocolate is completely melted. Spoon the chocolate into a zip-lock bag and cut a small hole in one corner. Working quickly, pipe the chocolate onto the lined try to form three discs, each about the size of a dollar coin. Immediately use the chilled wax seal to imprint the chocolate discs, holding on each for 5 seconds. Place the seal back in the ice (see Baker’s Tips) and repeat with the remaining chocolate making and imprinting three discs at a time. Set aside at room temperature to set and firm.
                        3. Once set use a small paintbrush to paint each disc with edible lustre gold paint to coat.

                          Chocolate Glaze

                          1. When ready to glaze the cake, carefully transfer the cake to a rack over a tray lined with baking paper. Return to the fridge.
                          2. To make the Chocolate Glaze. Place the gelatine sheets in a bowl and add 250ml (1 cup) of the chilled water to cover. Set aside.
                          3. Place the chocolate in a medium heatproof bowl. Combine the remaining 125ml (1/2 cup) water in a small saucepan with the sugar. Stir over medium heat until the sugar dissolves. Bring to the boil and boil gently, brushing down the sides of the pan with a pastry brush dipped in water to dissolve any sugar crystals, until the syrup reaches 104°C on a thermometer.
                          4. Remove the syrup from the heat and pour over the chocolate. Stir until the chocolate melts and the mixture is smooth.  Sift the cocoa powder over the chocolate mixture and use a balloon whisk to stir until combined and smooth. Add the cream and stir until the mixture cools to 60°C on a thermometer.
                          5. Use your hands to squeeze as much water as possible from the gelatine sheets and add to the warm chocolate mixture. Stir until dissolved.
                          6. Transfer the mixture to a jug anduse a stick blender to blend until the mixture is emulsified and smooth. Strain the glaze through a fine mesh sieve.
                          7. Once the glaze cools to 32°C on a thermometer pour it immediately over the chilled cake to create a smooth surface, allowing any excess to drip down the sides. Refrigerate for about 1 hour or until the glaze is set.

                          To Serve

                          1. Use a hot, dry knife trim the edges of the cake and then cut into 18 pieces (each about 7cm x 3cm). Transfer to a serving plate. Soften the reserved Chocolate Ganache by heating in 10 second bursts on high and stirring between each burst until smooth. Cool until almost a piping consistency. Spoon into a piping bag fitted with a small star nozzle. Pipe a rosette of ganache at the end of each cake portion and rest a Monogramed Chocolate Disc against the rosette to hold it. Decorate with gold leave and dust as desired.

                          Baker's Tips

                          • Paillette Feuilletine is fine broken shards of Crêpes Dentelle (a crisp biscuit made from rolled crêpes)and is used to add texture to confections and desserts. It is available from specialty food stores and French delicatessens.
                          • Edible lustre gold paint is available from specialty cake decorating shops and suppliers and some craft stores.
                          • The Hazelnut Praline Paste will be coarse crumbs in the beginning, but it will eventually get smooth with processing. Don’t add water to thin the mixture but a little vegetable oil can be added to reach the right consistency is needed.
                          • The longer the Chocolate ganache stands at room temperature the thicker it will become. It is ready to use when it becomes a peanut butter-like consistency. If left for too long, it will become too thick to spread.
                          • The wax seal must be left in the ice between imprinting the discs for it to work effectively and not stick to the chocolate.


                          Karthika based this recipe on one from