18 August 2012

Eight Layer Kahlua Cake (With A Rainbow Inside)

It's my sister's 18th birthday today, I can't believe it! I know she likes Kahlua, so I've been planning this cake for weeks and working out not only how to make it, but also how to make it in secret. This is a cake composed of eight layers of Kahlua-flavoured sponge with rainbow-coloured, Kahlua-flavoured buttercream in between, draped with a chocolate-nutella icing.

The outer layer of icing is Sweetapolita's Nutella Cloud Frosting, which is best made just before icing the cake, so that had to be left til last. Swiss meringue buttercream can be made in advance and frozen or chilled until needed, so I made it on Monday when I had accumulated enough egg whites (I've been making a lot of custard for breakfast lately, so each batch leaves two egg whites), then brought it back to room temperature last night before dividing it into seven and colouring each bowl of icing a different rainbow colour.

The sponge needs at least four hours in the freezer so that crumbs don't fly everywhere when icing the cake. I also needed to give them half an hour in the fridge after cooling in order to firm them up before slicing each in half, thereby turning four cakes into eight. Because of the time the cakes needed in the freezer, I was able to make them on Thursday night.

On Thursday night I was also going for a meal with everyone from work as I'm headed back to Newcastle on Tuesday and I'm unsure of whether I'll ever return to work there, dependent on finding french volunteering/interning opportunities and their duration, and if I actually find a job in the real world for when I've graduated. It was a great evening filled with laughter and Malibus-and-diet-cokes, and they gave me a going-away present, which touched me because I hadn't expected something like that at all, being just a summer worker and all.

Anyway, because of this lovely meal out and not finishing work til 5pm I was pushed for time with making the cakes. Luckily I managed to make all four cakes and left them cooling on the desk in my room while I was out so that nobody would see them. I think my sister could smell baking because she asked me what I was making, so I lied and said it was a cake for work. I think she bought it!

When I returned from the meal at some time after 11pm, I put the cakes in the fridge for half an hour before carefully slicing each one in half. As you can see from the picture below, not all of them were cut evenly, but since this was my first attempt at cutting cakes in half I feel it was a job well done, purely because nothing went drastically wrong. After wrapping the cakes in cling film I hid them at the back of the freezer and hoped my sister wouldn't go rooting around the freezer in the next 24 hours.

After dinner last night, when everyone else had gone to watch something dreary on the television, I put the cake together, jumping every time I heard someone/a dog approaching the kitchen, though luckily my sister stayed away. Somehow, despite all of the preparation, it still took me three or four hours to finish the cake off, but I'm very pleased with it and feel that this was time well spent!

I now have a confession to make: this cake doesn't have real Kahlua in it. I know, I've tricked you all, but don't you think 'Kahlua Cake' has a better ring to it than 'Tesco Soiree Coffee/ Cheap Kahlua Knock Off Cake'? Yup, me too. And at half the price of proper Kahlua, I was never going to shell out for the real deal.

This cake tastes great though, and the Kahlua/soiree coffee taste really comes through - just as well, considering there are seven shots in the whole thing! If you're looking to wow someone, this is the cake for you.

For the sponge:

  • 4 Shots (50mL) Kahlua (or cheap substitute)
  • 400g Butter
  • 400g Caster Sugar
  • 400g Self Raising Flour
  • 4 Eggs
  • 40mL Milk
  • 2 Tsp Baking Powder
For the Swiss meringue buttercream:
  • 400g Butter
  • 6 Egg Whites
  • 90g Caster Sugar
  • 2-3 Shots Kahlua
  • Gel Food Colouring (Red, Yellow, Green, Blue and Purple)
For the Nutella Cloud Frosting:
  • 460g Butter
  • 380g Icing Sugar
  • 4 Tsp Vanilla Extract
  • 250g Dark Chocolate
  • 200g Nutella
  • Preheat the oven to 200C/180C fan and line four sandwich tins with parchment paper. If, like me, you only have two sandwich tins then only make half of the cake mixture at a time, making the second half  only when you can use the sandwich tins because if you don't bake the mixture as soon as it is ready to go in the oven the cake won't bake as well as it should due to air escaping from the mixture.
  • Cream the butter and sugar together with an electric whisk for about a minute, until they form a light and fluffy mixture.
  • Beat in the eggs, one at a time, then sift in the flour and baking powder from a height to maximise the amount of air that is incorporated.
  • Gently fold the flour into the cake batter.
  • Add the milk and Kahlua and fold in until everything is well combined and the mixture has a soft dropping consistency.
  • Divide the mixture between the sandwich tins and bake in the oven for about 25 mins, or until a skewer comes out clean. Leave to cool on a rack, then put in the fridge for 30 minutes.
  • Remove the cakes from the fridge. It helps to have a cake turntable here, but if not you'll have to put more effort into cutting the cakes in a straight line. Place the cake on a turntable and, using a palette knife, carefully slice the cake in half horizontally so that you now have two cakes.
  • When all the cakes have been cut in half, wrap each one in cling film and put in the freezer (making sure that they can lie flat) for at least four hours.
  • To make the Swiss meringue buttercream, place the egg whites and caster sugar in a bowl over a pan of hot water, making sure that the base of the bowl does not touch the water. Put the pan over a low heat and whisk the egg whites with a fork until the sugar has dissolved - check by dipping your fingers into the whites and rubbing them together: if you can feel grains, your sugar has not yet dissolved.
  • Pour the egg white mixture into a large mixing bowl and use an electric whisk to whisk until stiff peaks can form and the bottom of the bowl is cool.
  • Make sure the butter is at room temperature, then slice it into small chunks. Whisk the butter into the meringue (egg whites mixture) a chunk at a time until you have a silky smooth buttercream. 
  • You can now store the buttercream in the fridge or freezer for up to two weeks, though make sure you bring it back to room temperature before trying to use it.
  • Divide the buttercream between seven bowls and colour the contents of each bowl according to the colours of the rainbow, i.e. one bowl red, one bowl orange, etc.
  • Again, it help to use a turntable to ice a cake but a standard plate will do. Remove the cakes from the freezer and unwrap one, placing it on a cake board or plate on the turntable, securing it it a spoonful of icing between the cake and the cake board. Put the violet (or dark purple) icing on top and spread it around so that there is an even layer across the top. Unwrap a second cake and place it on top, then repeat the icing process, this time with the indigo (light purple) buttercream. Repeat with the blue, green, yellow, orange and red, finally placing the last cake on top.
Yep, I may have forgotten to photograph the blue and red layers...
  • Now make the Nutella Cloud Icing. I will only give brief instructions here as I copied Sweetapolita's recipe completely, so you should check out her recipe for a better, more detailed description of what to do.
  • Whisk the icing and butter together, then whisk in the vanilla and slightly cooled, melted chocolate until fully incorporated. Finally, whisk in the nutella. You should have fairly stiff icing with a piping consistency.
  • Crumb coat the cake by dolloping the icing on top of the cake and spreading it over the top and down the sides of the cake. Fill in any gaps, but make sure this layer of icing is only just thin enough to cover the cake. Bravetart has a good video on how to do a crumb coat.
  • Put the cake in the fridge for 30 mins to let the crumb coat set, then cover with the rest of the icing. I used a palette knife to get smooth sides and a smooth top, scraping off the excess. The icing is a good piping consistency, though, so you can pipe the icing instead, if you wish.

For tips on the basics of cake making, take a look at The Basics. I won't pretend that this cake is good for you, but if you want to reduce the calories, if only by a fraction, take a look at Healthy(ish) Baking - though I will warn that you shouldn't reduce the sugar or use low fat butter in Swiss meringue buttercream as you will get a sub-standard icing.

I'm going to be super busy for the next few days - working, socialising, travelling to Newcastle, then moving - but I do plan on baking my new housemate a Carrot Cake, so I'll be posting another carrot cake recipe next week probably. Have fun in the mean time!

I'm entering this into the Bakespiration competition over at Stuck In The Tree.


  1. That is one amazing cake, what a heroic feat. Happy Birthday to your sister. I'm sure she'll be suitable impressed.

    1. Thanks, Choclette! She seemed quite surprised as I'd told her my present to her was a job at the restaurant where I work, and I think the cake was just what she liked. I'm so pleased!

  2. Super! You should enter this for lotties bake of challenge http://lottiesworldofcakesandbakes.eu/a-great-british-bake-off-blog-challenge/

    1. Thanks for telling me about the challenge! Is it similar to something from the Great British Bake Off, though? I don't watch it.

  3. What a beautiful cake, I bet the cake did not last long x


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