For the sponge cakes:
*all at room temperature
600g salted butter, at room temperature
600g golden caster sugar
3 tsp vanilla bean paste
12 medium free-range eggs, lightly beaten
600g self raising flour, sifted with 2 level tsp baking powder
For the buttercream:
500g soft unsalted butter, at room temperature
1kg white icing sugar
2 tsp vanilla bean paste
Food colouring of your choice
For the horn and ears:
Ice cream cone
Approx 350g ready to roll icing with yellow and pink food colouring to tint
Additional 500g buttercream in various pastel colours of your choice (we’ve used mint green, pastel pink, yellow, and baby blue for the rainbow piped mane)
A little black royal icing in a piping bag with a small round nozzle for the eye detail
Edible gold lustre spray, edible glitter
8” round cake tin/tins pre lined with baking parchment
8” round cake card
12” gold base drum in gold for display or cake stand of your choice
Large plastic piping bag / Large open star nozzle
**Set oven to 180 °C for fan oven or 200 for a conventional electric oven. Gas Mark 6.
Method for the sponge cakes:
Place the butter, sugar and vanilla into your mixing bowl and combine until mixed, then turn up the speed to high (or use a wooden spoon and plenty of elbow grease) and beat until the mixture is very pale, soft and fluffy and the granules of sugar have disappeared.
Add the beaten egg, about a quarter at a time. Mix this in slowly at each addition until all combined.
Add the flour gradually, a quarter at a time, mixing gently on slow until the dry flour has mostly mixed in. Fold with a metal spoon if you are doing this by hand. Just take care not to mix or beat vigorously or your sponge can turn out a bit tough.
Divide the sponge mix equally into 4 bowls, each bowl will be approx 600g each and colour with rainbow shades as required. I used pink, blue, yellow and green. Different brands of colours are stronger than others, so add a little at a time and stir gently until the shade of colour you like is achieved. It’s Now ready for the oven so place in your tins, if you only have one or two tins you can do this in stages. Each layer should take 20-30 mins depending on your oven, begin checking each layer after 20 mins. Remember all ovens vary so try to get to know yours and if in doubt get an oven thermometer too to check if your oven is older. To test the cakes, look for the signs, the cakes should be a light golden brown on the top and edges, springy to touch and if you want to be sure test with a sharp knife or metal skewer which should come out clean and free of mixture if they are cooked through. Turn out of the tin onto a cooling rack and allow to cool. Once cooled, trim the humped top of each later away to give you flat layers of sponge cake.
To make the buttercream:
Beat the butter and vanilla until soft, pale and creamy. Gradually beat in the icing sugar (using an electric or stand mixer is the easiest way but it can be done by hand) beating well between each addition until the buttercream is pale light and fluffy.
Set aside 1kg for the layering and filling, and for the mane detail, colour small amounts of buttercream in your choice of colours.
*To achieve the multi tonal effect, place small amounts of coloured icing into small thin plastic piping bags, then place these all together into a larger piping bag, with the ends snipped, pushed into a large star nozzle.
To make the horn and ears:
Colour 200g of the sugarpaste by kneading in some yellow food colouring.
Spread a little of the excess buttercream over the cone to aid sticking.
Roll out the sugarpaste to a long sausage, flatten with your hand and wrap around the ice cream cone, winding all the way up to cover and twist to a point. Leave to set for a few hours. Once dried add some edible gold shimmer spray if using.
For the ears:
Roll out approx 100g white icing to approximately 5mm thickness and cut two ear shapes using a knife.
Colour 60g of the sugarpaste by kneading in a little pink or red food colouring. Roll out slightly thinner than the white, and cut two smaller inner ear shapes. Stick these onto the white parts using a touch of water.
Pinch the bottoms together and add a couple of cocktail sticks into the bottom of each ear. Leave to set for a few hours.
To layer, crumb coat and cover the cake
Stick the bottom cake layer onto the 8” round cake card with a little buttercream and make it central.
Spread a layer of buttercream over the first layer, add the second sponge, and repeat with all 4 layers.
Using a palette knife, generously spread buttercream all around the sides of the cake, you can press on the top of the cake to hold it still, go all around filling in the gaps and smoothing over.
Once covered, spread a layer over the top, and then icing the palette knife, or a side scraper, sweep all around the cake with a firm pressure, keeping it straight to smooth off the excess and make as flat as you can.
With the palette knife, using a back and forth motion, smooth over the top to neaten. This is the first coat, pop in the fridge to chill for about 30 mins before covering with the second coat of buttercream.
Repeat the first coat steps again with the second coat to finish the covering.
Bringing the unicorn to life!
Stick the horn onto the top of the cake with some of your rainbow buttercream.
Place the ears either side.
Pipe on the mane detail with buttercream to give the multi rainbow tone effect. Start piping each swirl against the cake in little circles starting from the middle then piping around in a circular motion to create the rosettes covering over the top, sides and down the back of the cake or in any pattern you like.
To finish, pipe little eyes and eyelashes on the front of the cake to make the features, and lastly if you wish add a sprinkling of edible glitter.