Wednesday, February 5, 2014

Murasaki imo buttercream birthday cake

I'm currently looking for a space for my business (exciting stuff, what!), but the other day a friend asked me to make a special birthday cake for a friend.

After looking at various chocolate and carrot cake recipes I based the cake on this amazing 3-layered Victoria sponge cake by Peggy Porschen. I didn't want to use food colouring in this cake, and I didn't want to use quite as much buttercream as the original recipe, we also wanted something that looked more contemporary than classic, to match our friend's personality.

The gorgeous purple colour is all from powdered murasaki imo (purple potato) which is often used in confectionery in Japan (it is even a Haagen Daz flavour). I had most if 20g sachet left over from recent macaron experiments and didn't need the full amount. It imparts a very delicate sweet and earthy flavour to the buttercream, very nice. I also liked that you can still see the vanilla seeds in the mixture. 

A handy tip when using real vanilla beans is to rub the beans from the scraped pod into some of the sugar you are using in the recipe, in this case icing sugar in the buttercream, as it will help to avoid too many of the seeds clumping together.

Rubbing vanilla seeds into the sugar

The process of making the cake is very thoroughly explained in the linked-to recipe above. Here are some photos showing the step-by-step process as I took it. First trimming, filling and stacking the sponges. The first layer is spread with raspberry jam and the next with a portion of buttercream I'd kept separate from the murasaki imo powder.

Next came smoothing on a crumb-coat, an undercoat for the buttercream, to help make the final layer as smooth and straight as possible. Once you have the thin crumb-coat on, you chill the cake before applying the next layer.

Crumb coating of buttercream

While the cake was chilling between coats I had a bit of a practice piping the fleurs-de-lis on a dummy cake, but I rather feel that lots of practice is required to get the gracefully-sweeping shells of the original recipe.

Practice, practice...
Divide the cake in advance to know where to pipe

To avoid having too much buttercream on the cake, I topped it with a purple anemone (wind flower) I'd made out of gum paste somewhat loosely based on one I'd seen in the supermarket a few days earlier.

Just being the one flower I was able to bend the floral tape-wrapped wires around to make a kind of stand for it to lean on, so we could place it directly on top (usually you would insert a flower spike into the cake itself and put your fresh or sugar flowers into that plastic spike). The gumpaste rested on the buttercream just fine - I had wondered whether the moisture in the frosting would soften the gumpaste, but it held up fine when I tested a batch for 24 hours.

This was quite an extravagant version of a Victoria sponge cake. With the real vanilla, vanilla syrup-soaked sponges, multiple layers and lots of buttercream, it certainly fit the bill for an extra special birthday cake!

Making the vanilla syrup

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