Step 1

Preheat the oven to 170C/150C Fan/Gas Grease 4 x 20cm/8in sandwich cake tins and line the bottoms with greaseproof paper. Dust the tins with flour, then shake out the excess.

Step 2

To make the sponges, beat the butter and sugar together in a stand mixer or with a handheld electric whisk on a high speed until pale and fluffy. Turn the mixer to low speed and add the eggs bit by bit, mixing on high speed after each addition. Add the vanilla, then add half of the flour mixture. Mix until combined, then add the rest of the flour and mix until you have a smooth cake batter. Add the brightly-coloured sprinkles and fold them through with a spatula.

Step 3

Divide the cake batter between the 4 cake tins, filling each tin up to three quarters full. Bake for approximately 35 minutes, turning after 20 minutes so they colour evenly. Once baked, cool the cakes on a wire rack, then wrap in cling film and store in the fridge.

Step 4

To make the buttercream, place the salted butter in the bowl of an electric mixer. Sift the icing sugar on top, bring the mixture together at a low speed, then beat at high speed for a few minutes until the mixture is pale and fluffy. Add the vanilla extract and beat to combine.

Step 5

Put half of the buttercream in a separate bowl and add a dash of pink food colouring to it. Mix and add more colour if necessary, until the desired shade is achieved. The rest of the buttercream can be set aside at room temperature until later.

Step 6

Remove the cakes from the fridge and trim the domes off so they are flat. Discard the off cuts. Place the 18cm/7in non-slip mat on the turntable and put the 20cm/8in cake board on top. Put a dab of pink buttercream on the cake board and place one of the sponges on top. Spread a 1cm/½in thick layer of buttercream on the top of the sponge. Place the next sponge on top and repeat this process until you have assembled the 4 sponges on top of one another with 3 layers of buttercream in between. The final top sponge should have the base facing upward. Gently press the top of the stack to ensure the cake is level and free of air bubbles. Place in the fridge for 10 minutes.

Step 7

Using a knife or a cheese grater, trim the sides of the cake to within a few millimetres of the cake board it’s sitting on. Add a splash of milk to the plain-coloured buttercream and beat again for about 30 seconds. Put 2 spoons of the buttercream on top of the cake, then spread the buttercream towards the edges and down the sides with a palette knife. Scrape off any excess and discard. This layer should be very thin, almost translucent in parts. Return the cake to the fridge for 10 minutes.

Step 8

Put the 25cm/10in non-slip mat on the turntable and place the 30cm/12in cake board on top, along with the cake. Place all but 3 tablespoons of the buttercream on top of the cake. Gently rock the palette knife back and forth to disperse the buttercream and turn the turntable in the opposite direction to that which you are spreading. Spread the buttercream evenly over the top and down the sides of the cake. Scrape the excess buttercream off the sides of the cake using the side scraper. Turn the turntable in a fluid motion while ensuring you keep the blade at a 45 degree angle against the side of the cake with your other hand. Repeat until you have a nice smooth finish.

Step 9

Using your palette knife, carefully brush any excess buttercream that’s gathered at the rim of the cake towards the centre, aiming all the time for sharp edges, straight sides and a flat top. If the buttercream has ‘torn’ in places, dip your palette knife in hot water and use that to smooth over any imperfections. Put the cake back in the fridge for 10 minutes, or until you’re ready for the next stage.

Step 10

Put the cake directly on the turntable. Apply the remaining 3 tablespoons of plain-coloured buttercream to the lower third of the cake in a rough pattern, then press the pastel sprinkles into the buttercream. It helps to have a bowl underneath to catch the falling sprinkles!

Step 11

Beat the rest of the pink buttercream and place it into the piping bag fitted with the star nozzle. Pipe six swirls on top of the cake and sprinkle them with the remaining sprinkles.