Method

• 1.
  Preheat oven to 150°C. Grease and line two 20cm square cake pans with baking paper.

• 2.
  Using a stand mixer, beat butter and sugar over medium-high speed until thick and pale. Add the vanilla, then add the eggs, 1 at a time, beating well after each addition. Reduce speed to low, then add one-third flour, then one-third milks. Repeat, alternating between flour and milks, beating until combined.
• 3.
  Divide the batter among 6 bowls. Add a few drops of different food colourings to each bowl and stir to combine (you may need to use a few more drops to achieve the desired colour depending on the brand). You should have separate yellow, purple, red, green, blue and orange cake batters. Dollop spoonfuls of different coloured batters in each cake pan until all batter is used. Using a knife, swirl the mixture in the pan to create a rainbow effect. Be careful not to over mix the colours.
• 4.
  Bake for 40 minutes or until a skewer inserted into the centre comes out clean. Cool cakes in pans for 10 minutes, then turn out onto a wire rack to cool completely.
• 5.
  Meanwhile, for the ganache, place the chocolate in a heatproof bowl. Place the cream in a small saucepan over medium heat. As soon as cream mixture bubbles around the edge, immediately pour over chocolate. Set aside for 5 minutes to melt, then stir until smooth. Set aside to cool and thicken.
• 6.
  Using a serrated knife, trim the tops of the cakes to level. Place one cake layer on a board. Spread jam over the top, then sandwich with the remaining cake layer. Trim the sides of the cake to create a perfect square, then cut into 9 equal squares.
• 7.
  Place ganache in a shallow bowl and shredded coconut in a separate bowl. Coat sponge in ganache, then roll in coconut. Set aside on a wire rack to set, then serve.