Method

• 1.
  Preheat the oven to 175°C (350°F). Grease three 23 cm (9 in) round cake tins, then dust with flour, tapping out the excess.
• 2.
  Chop the butter into small, pea-sized pieces and return to the fridge. Bring the milk to room temperature by zapping it in a microwave for 30 seconds, then add the vanilla and set aside.

• 3.
  Using an electric mixer, beat the flour, baking powder, salt and 500 g (1 lb 2 oz) of the sugar on low speed for 30 seconds to combine. Add the cold butter, then increase the speed to medium and beat until the butter breaks down and the flour mixture is the texture of wet sand. Reduce the speed to low and beat in the milk mixture.
• 4.
  In a separate clean bowl, whisk the egg whites and remaining 300 g (10 ½ oz) of sugar on high speed until soft peaks form. Gently fold the meringue into the flour and milk mixture until well combined.
• 5.
  Divide the batter evenly among the prepared tins and bake, rotating halfway through, for 30–40 minutes or until golden and a skewer inserted into the centre comes out clean. Transfer the tins to a wire rack for 10 minutes before turning the cakes out of the tins to cool completely.
• 6.
  Meanwhile, to make the frosting, using an electric mixer, beat the butter until smooth, making sure to stop the mixer every so often to scrape down the sides and bottom of the bowl (it’s important the butter is nice and soft so you don’t get any clumps of cold butter when piping the frosting). Add the cream cheese, one-quarter at a time, beating on medium speed until well combined. Beat in the vanilla and food colouring, then reduce the speed to low and gradually add the icing sugar. Crank up the speed to high and beat for 30 seconds or until well combined and fluffy.
• 7.
  Using a large serrated knife, trim the tops off the cakes to make them level. Frost and stack the three layers, then frost the sides. Decorate the sides with rainbow sprinkles.