I can easily say I won't be rushing to make this sort of cake again. It took about 7 hours from start to finish, and I was knackered by the end of it - and I didn't enjoy the process. The cake was fine to make, but the French buttercream - what a faff. It was divinely smooth, but oh-so-rich - too buttery for my liking. And a real skill to master (I think I bodged it in the end). You might also notice a deliberate mistake from the photograph - I ran out of raspberries. Although several people at cake club thought it was meant to look like that - modern art if you like - I could've got away with it!
For the kirsch syrup
100g caster sugar
3 tbsp kirsch
For the sponge
3 egg whites
15g caster sugar
100g ground almonds
100g icing sugar
30g plain four, sifted
30g butter, melted
For the chocolate ganache
100ml double cream
100g dark chocolate
For the French buttercream
3 egg yolks
75g caster sugar
225g butter, cubed and softened
2 tsp vanilla paste
200g seedless raspberry jam
For the kirsch syrup, tip the sugar into a small pan. Add 200ml water and cook over a medium heat until the sugar has dissolved. Bring to the boil and simmer for 4-5 minutes, or until the syrup has reduced by half. Remove from the heat, add the kirsch, stir and leave to cool completely.
For the sponge, heat the oven to 220C/Fan 200C. Grease and line a 33x23cm Swiss roll tin with baking parchment. Whisk the egg whites in a bowl until stiff peaks form when the whisk is removed from the bowl. Add the caster sugar, one teaspoon at a time, whisking between each addition to make a glossy meringue. Cover with cling film and set aside.
Tip the ground almonds and icing sugar into the bowl of a food mixer and add the whole eggs. Whisk together for 3-5 minutes, or until doubled in volume. Fold in the flour, and then gently fold in the meringue in three separate batches. Pour the melted butter down the side of the bowl and fold in, until incorporated. Tip the mixture into the prepared tin. Bake for 5-7 minutes until pale, golden-brown and springy to touch.
Place a sheet of baking parchment over a cooling rack and turn the cake out onto it. Peel off the baking parchment from the base of the cake and leave to cool completely.
For the chocolate ganache, pour the cream into a small pan and heat until just bubbling. Remove from the heat and add the chocolate. Stir until all the chocolate has melted and mixture is smooth and glossy. Pour into a bowl and leave to set.
For the French buttercream, place the egg yolks in the bowl of a food mixer. Whisk until pale and fluffy. In a pan over a gentle heat, dissolve the sugar in three tablespoons of water and then boil it steadily until the syrup reaches 110C on a sugar thermometer. With the food mixer running, slowly pour the syrup over the egg yolks. Continue whisking until the mixture is thick and mousse-like. Add the butter, a little at a time, whisking continuously and finally add the vanilla paste.
Make sure the sugar isn’t too hot. If it is, it will solidify the second it hits the bowl or the whisk. This happened to me the first time - I had a second go, making sure the sugar didn’t get too hot (I think my sugar thermometer is unreliable so I just watched it).
To assemble, slice the cooled sponge horizontally so you have two 33x23cm sponges. Cut each of the sponges in half vertically, so that you have four sponges.
Place one of the sponges on a cake board and brush with some of the kirsch syrup. Spread over some of the French buttercream with a palette knife. Top with another sponge and brush with kirsch syrup, then spread over the chocolate ganache.
Top with a third sponge and brush with more kirsch syrup. Spread over more French buttercream. Top with the final sponge. Brush with the remaining kirsch syrup and spread with the remaining crème au beurre.
Arrange the raspberries over the top in rows and brush over the melted jam to glaze. Refrigerate the opera cake for at least two hours to set the layers and make it easier to trim. Trim the edges using a sharp knife to reveal the layers.
This is a recipe from BBC Food.
I won't be making it again, although everyone thought it was lovely. It was too rich for me. Give me a Victoria sponge any day.