Monday, June 23, 2008

Gateau Opera

My last recipe (for a while) from the excellent One Perfect Ingredientby Marcus Wareing. This is the very last recipe in the book and, unlike the others, actually is a bit of a bother.

But it's worth it.

Well, I would say that because it's cake. Not just any cake, but Gâteau Opéra. Apparently created in honour of the Paris Opéra in the 1930s, Wareing's version is a coffee, chocolate and butter cream cake that's exceptionally good.

I had two goes at this, because my father volunteered me to make the birthday cake for my grandma's 90th. The first effort resulted in four huge portions of cake ... which were very good, but not particularly dainty and totally unsuitable for handing around to about 40 guests.

The cake is made in parts: sponge, ganache, buttercream and a glaze. The order in which you make these parts is incidental - the first time around I made the sponge last, but for the big event I made the sponge first.

So, let's start with the sponge. Cream together 100g soft unsalted butter, 100g caster sugar and add 2 medium eggs. When well combined add 100g plain flour, sifted with 1 tsp baking powder. Finish with 1tsp of instant coffee dissolved in 1 tsp hot water.


The tricky part is baking this. You need to bake it in a preheated oven (160C fan, 180C) in a 22x36cm rectangle for 4-5 minutes, or until done. What you're aiming for is a very thin (but still light) sponge, that is nice and flat. On my first pass, my sponge was far too thick (hence the monstrous final cake). Second time around, I used a much larger baking tray (baselined, of course) and just spread the mixture across it. This was much more successful.

Once the sponge is done, leave it to cool in the tray and move on to the other parts.

Next - the ganache. Scald 100mL of whipping or double cream, take it off the heat and add 100g of dark chocolate, chopped. Beat until the chocolate is fully melted and finish with 20g of soft unsalted butter.

The buttercream is the really tricky part, and I'm still not entirely happy with how mine turned out looks-wise. Fortunately, looks don't matter, as it will be sandwiched between cake and ganache.

Beat 1 egg with 2 egg yolks, until thick. In a pan, dissolve 75g of caster sugar with 2tbsp of water and boil for 3 minutes. Now ... Wareing's recipe says to turn off the heat and allow the bubbles to disappear before beating the sugar syrup into the eggs. When I did this I found the sugar was too cool and I ended up with toffee stuck to the end of my whisk. My solution was to just pour the sugar in, hot and bubbling. Now, you need to keep on beating so you don't end up with scrambled sugary eggs. If you're doing this by hand, I feel really sorry for you. If you're using a stab mixer with a whisk attachment (as I did the first time) it will still be hard work. Use a Kenwood Chef and it's pretty painless. Once your sugar is all mixed in and the mixture is starting to cool, beat in 125g of unsalted butter, softened and diced. Finish the cream with 1 tsp of instant coffee dissolved in 1 tsp of hot water.

My mixture tasted FAB but did look a little curdled. I suspect had I followed the instructions more to the letter (beat the sugar and eggs until completely cool, and then add the butter, for example) it might have looked a little prettier. But the fact is, I stayed sane, I didn't shout at anyone and it tasted really really good.

Finally, the glaze. I actually passed on this for my final cake as the first time round I wasn't happy with the consistency or appearance. Scald 1tbsp of whipping/double cream, remove from the heat and add 25g of dark chocolate. Dissolve 10g of caster sugar, with 1 tsp of cocoa, a further tbsp of cream, and 50mL of water. Simmer for 2 minutes and then strain on to the chocolate and cream mix. Mix until smooth.

By the time you've done all of this this, your sponge will be cool - if you made it first. I tend to make the sponge and fillings the day before and then assemble the next day. It breaks the process up a bit. If you do this, DON'T refrigerate the filllings, as they'll be impossible to spread!

Take your sponge and spread with the buttercream. The aim is to have an even, flat layer of buttercream. You use all the buttercream. You don't need to do this again.

Refrigerate the cake for at least half an hour.

Now spread the buttercream with the ganache. You need to be a little careful here: don't rush. Again, use all the ganache to form a flat, even layer.

Refrigerate the cake.

Now you need to decide how big or small to make your cakes. Marcus Wareing opts for stacks three high: doing this I ended up with just four portions! For grandma's birthday, I only made stacks that were two high. Much daintier.

You need to cut the cake into the right size cubes (use a hot knife, and I found that using a chef's style knife easier than using a long thin knife, like a ham knife). Stack your cubes of cake, top with the glaze if using, and refrigerate until ready to serve.

The flavour improves and the cake keeps really well. I also enjoyed eating it a lot more when it was at room temperature rather than straight from the fridge. Wrapped in foil and taken to work for afternoon tea it develops a really delicious sticky, gooey character ...

Yes, it is a fair bit of work, and quite fiddly - but I think quite worth it!

Here's a summary of the important bits:
  • you're aiming for a thin sponge. Not so thin it turns into a biscuit, but the thinner and flatter it is, while still being a bit cake-y - the better.
  • don't refrigerate the buttercream or the ganache - you'll struggle to spread them
  • DON'T RUSH - break up the making of the cake, as you really won't be able to spread the ganache over the buttercream if it's not set, and you won't be able to cut the cake if the ganache isn't set
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