Ever since we first heard about these surprising, tricky and colourful cakes Elldrew have been itching to try their hand at the much fabled Rainbow Cake; so an invitation to an English Easter tea party was the perfect excuse. Our hosts are renowned as excellent cooks and so not wanting to leave anything to chance Elldrew scoured the internet for tips on ensuring the perfect cake. We’re glad we did, but we’re also glad that we used our experience and instinct to add a little Elldrew magic – being the selfless souls that we are we thought we’d save you all that googling and instead provide Elldrew’s guide to baking the perfect Rainbow Cake (with thanks also to Kerry Cooks from whom we took a lot of our inspiration).
This blog is a long one, so get comfortable.
Firstly a good Rainbow Cake is a labour of love and one which takes planning and preparation, as it is effectively 6 cakes plus an extraordinary amount of icing, so we’d suggest reading this through once or twice before you start; probably best to read it with a glass (or bottle) of wine. To make your life a bit easier you can also make the cake in several stages; this is the timetable that worked best for us:
- Baking: One week (or as long as 1 month) before the “cake cutting date” put aside an afternoon and bake the sponges. Once baked and cooled, wrap them carefully and individually in cling wrap and freeze.
- Icing: The night before (or perhaps two nights before) the “cake cutting date” make your icing (this is easy and takes maybe half an hour max). Cover and refrigerate.
- Assembly: The day of the “cake cutting” assemble and ice the cake (more on that timing below). This could also be done the day before as the icing will act as a seal and prevent the cake from drying out. You need a good 2-3 hours to do this, but there’s lots of stopping and starting so you can do other jobs in between.
Once you have your timings worked out then you also want to make sure you have everything you need to hand. As well as the usual baking paraphernalia and ingredients we would encourage you to have the following:
- Enough baking tins to bake each layer separately:
- It’s unlikely you have six (or even seven) identical tins and so we used a set of disposable foil flan/baking tins. We got them from our local pound shop for £1 for 6 tins. For £1 we threw them all away afterwards but you could probably clean them and re-use them. If you don’t have 6 tins you are going to need a lot longer to bake all those layers!
- You can use 6 inch, 7 inch or 8 inch baking tins with this quantity of ingredients. We used 8 inch and so we had a larger, flatter cake; a 6 inch tin would be smaller but higher. We had the choice of 6 inch or 8 inch tins in our pound shop but as we were displaying it on a 10 inch cake plate we wanted the larger diameter. We also think it slices more elegantly, but that’s just our opinion.
- Enough bowls (mixing bowls, table bowls, whatever you have to hand) to divide the batter so you can colour each layer.
- The correct food colouring. Those little bottles of liquid colour won’t work. The colour won’t be rich enough unless you add so much that it ruins the batter. You need colouring powder or gels, and really, the proper professional ones. We haven’t tried them but lots of people comment that the supermarket “gel colourings” are also too weak. A few years ago we splashed out on a set of Wiltons food colouring gels. They’re great, a little goes a very long way and they got us exactly the right colours in our Rainbow Cake.
- Digital scales. They’re really going to help to divide the batter for each layer. The more even the weighing, the more evenly sized each layer (but if you’re not that bothered then old fashioned scales will still get you pretty close).
R is for Ready
Having read all the above, are you now ready to start your Rainbow Cake? If so, then here goes:
Step One: Baking
Essentially, the cake is just layers of a classic sponge cake. There’s lots of variations on this but we’ve always been super successful with Mary Berry’s Victoria Sponge recipe – it’s light, fluffy, moist, flavoursome and easy to scale the quantities up, so that’s the recipe that we used. We had some concerns that the sponge would be too light to support all 6 layers (and the icing) but we worried for no reason.
350g softened unsalted butter
350g caster sugar
6 large eggs
350g self-raising flour (sifted)
3 level tsp baking powder (sifted)
- Pre-heat the oven to 180°C/Fan 160°C/gas 4 and take your butter out of the fridge to soften (we often let it stand on the radiator and that seems to get it to the right texture – just make sure it’s in a bowl; nothing worse than molten butter running down the middle of a radiator!).
- Grease each of your baking tins and line the base with baking paper. Take a bit of time to do this as it’s important that they’re both well greased (disposable tins aren’t non-stick after all) and that the lining on the base is as flat as possible (the layers are pretty thin so you don’t want any nasty wrinkles from something as simple as a piece of flat greaseproof paper).
- At this point weigh whatever bowl you are going to mix the cake ingredients in (whilst it’s still empty). Write the weight down.
- Mix up your cake batter however you normally do this; for Elldrew we cream the butter and sugar first, then add the eggs (at room temperature) and lastly sift in the flour and baking powder (so that’s a second sifting; the first one should have been when you weighed it out) and beat until blended.
- Take care here not to over beat – you’ll need to beat the mixture again when you add the colouring.
- Now weigh the bowl with all the blended ingredients in it so that you can work out the exact weight of the ingredients (remember how you weighed the bowl empty earlier – now you know why).
- Now you need to divide that cake mixture evenly between those 6 bowls that you got out earlier for this purpose. I know, this bits annoying and fiddly but, as I said earlier, the perfectionist in us wanted to make sure it was perfect.
- Each bowl/layer can now be coloured as required. This is pretty easy using those gel colours we mention above. Note that the colours remain consistent once baked so make sure the batter looks the colour you want it to.
- Once each layer is coloured then pop the mixture into the prepared baking tins and level out.
- Bake in the pre-heated oven for about 25 minutes or until well risen and the tops of the cakes spring back when lightly pressed with a finger.
- Leave to cool in the tins for a few minutes then turn out, peel off the parchment and finish cooling on a wire rack.
- Once cooled you can trim the top of each layer to ensure they are even sizes and reasonably flat. You can also use this as an excuse to taste the “trimmings” to check the flavour of the cake.
- If you’re following Elldrew’s timeline then once cooled, now’s the time to wrap each layer separately in cling wrap and pop them in the freezer until ready to bake.
Step Two: Icing
We used a simple cream cheese frosting (based on a tried and tested Hummingbird bakery recipe) although Elldrew are confident that any other type of frosting would work equally well. The quantity below makes a generous amount of frosting – quite a bit more than is really necessary but given the cheap ingredients we would prefer to have a bit “too much” than “not quite enough” icing.
150g unsalted butter, at room temperature
375g cream cheese, cold
900g icing sugar, sifted
- Meanwhile, make the frosting by beating about 90% (~800g) of the icing sugar with the butter until the mixture is well mixed.
- Add the cream cheese in one go and beat it until it is completely incorporated. Taste the frosting and add more sugar to taste.
- Turn the mixer up to medium-high speed and continue beating until the frosting is light and fluffy (this takes around five minutes).
- Do not over beat, as it can quickly become runny.
- Cover the frosting with cling film and refrigerate overnight.
Step Three: Assembly
Elldrew recommend ensuring you have ample time for the assembly. Time lets you refrigerate the cake in stages which helps to ice it neatly – it is a little fiddly and we would prefer not to do this in a rush. Elldrew also recommend noting down the order you want the layers and remember that the last layer is the bottom layer (so if you’re following a conventional rainbow then the purple/violet layer is the bottom layer).
- Take the first two cake layers out of the freezer around 20 minutes prior to frosting (purple and blue layers in our case). We found that this kept them firm enough to ice easily but flexible enough to be able to stack them neatly.
- Put a couple of small blobs of the cream cheese frosting on the plate or cake stand you’ll be using to adhere the first layer of cake. This helps secure it firmly onto the board.
- Pop the first layer (that purple one) onto the centre of the plate, and then apply a thin layer of cream cheese frosting as evenly as possible. There’s a lot of frosting on the whole cake so you really only want a very thin layer between each cake – just enough to be able to see it when you cut the cake.
- Put on the next layer (the blue layer) and pop the whole cake and the bowl of frosting back in the fridge for 20-30 minutes to firm up. Take the next two layers (green and yellow) out the freezer.
- After 20ish minutes repeat with the next two layers. Refrigerate and remove the final two layers (orange and red) out the freezer.
- After another 20-30 minutes, layer on those final two layers and return to the fridge.
- 30 minutes later remove the cake and the frosting from the fridge. Fill in any big gaps between the layers and then provide a very thin layer of frosting all around the sides and top of the cake using a palette knife. If you’re an expert baker you’ll know that you are applying a crumb coat. For non-expert bakers this technique is to seal in the crumbs so that they won’t get into (and spoil) the final thicker coat – for a Rainbow Cake this is really important if you want that lovely white finish and not a grainy icing with lots of multi-coloured crumbs. This coating should be really thin and you’ll still see the cake through it. That’s fine – you should still have loads of frosting left, just put it all back in the fridge and leave it for around an hour.
- After the hour, you can apply that second and final coat of frosting. This can be nice and thick to cover the colours of the cake (but not too thick, remember my earlier comment about there being lots of frosting).
- If you’re an expert with all the right equipment then you can probably get a lovely smooth finish. If you’re like Elldrew who don’t have anything as fancy as a cake turntable, or scraper etc then we just used our palette knife to smoothen out and neaten the surface. If you’re really creative then you can use decorations to hide any blemishes (we’re not saying we did that at the base of the cake just that we might have done!).
- Refrigerate for another hour or so for the icing to set and then it’s ready to serve.