Hazelnut Opera Cake

Cheers to a new year! I hope you have enjoyed the festive season, and all pumped for the new year? I know I am! Bring it on 2016!

This is my first blog post of the year. So it should be about cake. Of course.

This one I'm excited about. Hazelnut Opera Cake. My take on the classic opera cake.

My hazelnut opera cake consists of 5 components - hazelnut joconde, coffee kahlua syrup, nutella spread, coffee buttercream and chocolate ganache glaze.

I found that getting the ratio of the components right is the trickiest part of making this cake, and also the most important as it has a huge impact on the overall balance of flavours. I tried to make the joconde and buttercream the same thickness at about 5mm. For the nutella layer, I found that it's best to keep it about 1mm or it can be too sweet and overpowering.

I kept the decoration simple with a light sprinkle of coffee beans, cocoa nibs and almond meal.



Hazelnut Opera Cake

Makes one 15cm cake

Hazelnut Joconde
125 grams icing sugar, sifted
125 grams ground hazelnut (hazelnut meal)
40 grams plain flour, sifted
160 grams whole eggs, room temperature
30 grams unsalted butter, melted and cooled
100 grams egg whites (reserve yolks for the buttercream)
30 grams caster sugar

Coffee Kahlua Syrup
125 ml water
80 grams caster sugar
125 ml espresso
2 tablespoons kahlua

Coffee Buttercream
2 teaspoons coffee granules
2 teaspoons hot water
60 grams egg yolks
100 grams caster sugar
30 ml water
225 grams unsalted butter, softened, cut into small cubes

Chocolate Ganache Glaze
125 grams dark chocolate
20 grams liquid glucose
130ml whipping (pouring) cream

You will also need Nutella.

To make hazelnut joconde:
Preheat oven to 200 degrees celcius conventional (or 180 degrees celcius fan-forced). Line two 35 x 22cm baking trays with baking paper.

Using an electric stand mixer fitted with whisk attachment, whisk icing sugar, hazelnut meal, flour and whole eggs for 10-12 minutes until the mixture is light and aerated. With the mixer still running, slowly add cooled melted butter to the mixture until incorporated. Set aside.

Using an electric stand mixer, with a separate clean dry bowl and whisk, whisk egg whites until foamy. Gradually add in caster sugar and whisk until stiff peaks form.

Using a spatula, fold in a third of the stiff egg whites into the hazelnut batter to loosen. Carefully fold in the rest of the stiff egg whites.

Spread the mixture onto the prepared baking trays to about 5mm in thickness. Bake until golden brown and the sponge springs back when pressed gently. This should take about 12-15 minutes.

To make coffee kahlua syrup:
In a small saucepan, bring sugar and water to boil, and cook for 1 minute. Remove from heat, add espresso, and leave to cool. Add kahlua.

To make coffee buttercream:
Combine coffee and water, set aside.

Place yolks in the bowl of the electric mixer fitted with whisk attachment.

In a small sauce pan, bring caster sugar and water to boil without stirring. When the temperature of the syrup reaches 115 degrees celsius, remove from heat, start mixer at high speed, pour the syrup in a thin stream into the yolks, and whisk until thick and cools completely. It should take about 10 minutes.

Start adding small lumps of the softened butter a little at a time, whisking well after each addition and scraping down the bowl from time to time. When all the butter has been incorporated, add coffee mixture, and continue to beat until light and aerated.

To make chocolate ganache glaze
(Note: Make this after you have assembled the cake and the cake has been allowed to firm up in the fridge for at least 1 hour. You will not need to use all the glaze.)

Melt chocolate over bain marie or in microwave.

Stir glucose and cream in a small saucepan over medium heat until glucose dissolves and mixture comes to a gentle simmer. Remove from heat. Gradually add hot cream to the chocolate, mixing continuously to form an emulsion. Let cool slightly (about 5 minutes). Use immediately.

To assemble:
Cut hazelnut joconde into 3 squares (about 17 x 17cm).

Place one of the squares on a baking paper, brush square generously with the coffee kahlua syrup. Spread a layer of nutella (about 1mm thick). Spread coffee buttercream over (about 5mm thick). Repeat with second square, syrup, nutella, buttercream. Repeat with last square, syrup, buttercream.

Cut the cake with a 15cm cake ring. Leave the cake in the ring, remove scraps, and place in fridge to set for at least 1 hour.

Prepare chocolate ganache glaze, pour a thin layer on top of cake, give the cake a few firm taps on the kitchen bench until the glaze evens out, return cake to fridge for at least 1 hour. Demould and serve.