Gateau opera, in a nutshell, is a chocolate and coffee cake. It consists of three main components: A joconde sponge, or almond sponge, layers of coffee buttercream and a rich and velvety chocolate ganache. I do find myself to be quite particular about how the things I bake look on the plate these days and what I always do is a quick google image search to find some inspiration. Sadly 90% of what I saw (or more) simply did not fascinate me. And having spent some time researching the recipes, I decided to change the recipe slightly in an attempt to produce a better looking cake. Normally, the recipe would require a coffee syrup to be brushed onto the sponge layers but I find that doing this would produce a sort of dirty looking sponge due to the colour from the coffee powder. I substituted the coffee powder with rum instead, which in my opinion never goes wrong with chocolate anyway, and best of all it's colourless so I could preserve the natural golden colour of the sponge. The second thing that I changed was the flavour of the chocolate ganache, if you've read my previous entries you'd have known that I am now a big fan of earl grey and chocolate, and so I decided to add some depth of flavour to my ganache by infusing the cream with some earl grey. Lastly, most recipes call for the use of chocolate ganache (same thing used in the layering of the cake) for the top. Being particular about presentation as always, I decided to go with a more glossy chocolate glacage instead. That way I would get a better finish and produce a shiny surface at the top, like this:
This was also my first time piping words and drawing treble clefts on a cake. Some turned out better than the other.
The making of the cake itself took me a while, partly because I was making two batches of croissants on the very same day and it was manic in my tiny kitchen. There were a million mixing bowls everywhere since I had to make the buttercream and ganache separately. The joconde sponge had to be baked in two batches as well but I had no space to cool them on. I'd pretty much utilised every surface I could find in the kitchen, the top of the fridge, the microwave, except the floor for health and safety reasons of course. I was so knackered by evening I just couldn't get myself to make the glacage and so I just left it in the fridge covered for the next day.
It turned out my friend was coming over to make some profiterole swans with me the next day having seen the pictures I put on facebook. It was a fun afternoon but it did last 5 hours with lots of snacking and chatting. And so all I could manage on the day was the glacage but I decided to pipe the words 'Opera' the next day. I didn't want to do something for the very first time while feeling exhausted. After all, I had spent so much time constructing this cake I'd be devastated to ruin it with horrible piping.
Anyway thank God it finally turned out very close to what I had in mind. Taste wise, it was good. But I forgot to add the earl grey to the glacage so I didn't manage to make it taste exactly the way I wanted. But that said everyone who came over for tea thought it was a good looking chocolate and coffee cake so I'm quite happy!
Things I would have done differently:
1. Brush the joconde more liberally with the rum syrup for a more moist cake and more rum flavour.
2. Make more buttercream and ganache for easier spreading during the assembly of the cake.
3. Ensure I don't spread any buttercream or ganache on the top layer sponge to get a smoother finish.
4. Don't forget the earl grey in the glacage!
A friend of mind suggested piping words and the treble cleft on a marble surface and let cool before using them as 3D decorations and I can't wait to try that out. What an ingenious idea I must say!
Gateau Opera recipe: Makes a 15cm x 10cm rectangular cake
45g egg yolks
187.5g soft butter
6g coffee powder
Bring the milk with half the amount of sugar to a boil. Meanwhile, whisk the yolks with the other half of sugar until pale and temper them with the hot milk, whisking all the time. Return the mixture to the saucepan and cook until 85C or when a custard forms. Be careful not to overcook it or else it will curdle. At this stage you could strain the custard to remove lumps or just skip this step if your custard looks smooth. Whisk until the mixture has cooled down and incorporate the coffee powder and butter until it forms a smooth buttercream. Wrap with cling film and leave to cool at room temperature.
Chocolate earl grey ganache
120ml double cream
8g of earl grey tea leaves
120g dark chocolate, melted
Bring the double cream to a boil and add the earl grey. Cover with a lid and leave to infuse for 10 minutes. Strain the cream into the dark chocolate and butter, stir until glossy and well combined. Wrap with cling film, ensuring it touches the surface of the ganache and leave to set at room temperature.
1 tbsp of rum
Melt the sugar in water until a syrup forms. Stir in the rum. Leave to cool.
For the joconde sponge:
85g ground almond
75g icing sugar
25g cake flour (or 20g flour and 5g cornstarch)
150g whole eggs
90g egg whites
10g caster sugar
30g warm melted butter
1. Whisk the whole eggs with icing sugar until it's pale yellow and smooth.
2. Sift and fold in the ground almond and cake flour.
3. Ladle some of the egg mixture into to bowl of warm melted butter, mix until thoroughly combined.
4. Mix in the butter mixture.
5. Whisk the egg whites with caster sugar until stiff peaks form.
6. Fold in the egg whites.
7. Spread the batter as thinly as possible on a parchment paper, placed on a baking sheet or you can use the bottom of a baking tray. Bake at 250C for 5 to 7 minutes until they are starting to brown. These almond sponge are very thin and so bake extremely quickly. You have to keep an eye on them at all times.
8. Cool the sponge until just warm to the touch and sprinkle icing sugar all over. Flip the sponge onto another parchment paper and peel away the paper. You may have to bake the batter in two batches.
9. Cut the sponge into 15cm x 10cm rectangles, you should have about 8 of them.
Place a piece of joconde sponge on your work surface. Brush it liberally with the rum syrup and spread over the buttercream evenly. Place a second piece of sponge on top and brush again with rum syrup, followed by a layer of chocolate ganache. Repeat this alternating layers of buttercream and ganache until you reach the final piece of joconde sponge where you brush it with the rum syrup and wrap in cling film to chill in the fridge for 3 to 4 hours or even overnight.
Meanwhile, prepare the chocolate glacage:
½ tbsp powdered gelatin or 2 sheets gelatin
¼ cup (60g) heavy cream
5tbsp (60g) granulated sugar
¼ cup (50g) water
1/3 cup (30g) unsweetened cocoa powder5g earl grey
Soften the gelatine in cold water.
Boil cream, sugar, water, cocoa powder and earl grey leaves. Take off heat and let cool slightly before adding the softened gelatine leaves. The glacage is best used at 28-33C, you can warm it up in a Bain-Marie if it gets too sludgy.
Pour the glacage over the cake and spread evenly using a spatula. It should even out very easily with some sweeping motion from your spatula. Leave to stand for a few minutes and leave to chill in the fridge for a couple more hours.
To pipe the word 'Opera', simply melt some dark chocolate and spoon them into a cornet (basically a cone made with parchment paper) and practise it a few times on a plate before doing it on the cake.
This cake should be great if you wish to impress at an afternoon tea, perhaps with a few profiterole swans lying around too.
The next time I make this gateau opera I would be decorating it with 3D chocolate letters and some edible gold leaf, to create the sense of occasion for my beloved grandma.