• Preheat oven to 180°C fan forced and line a lamington tray with baking paper.
• In a bowl, mix self raising flour and baking powder together. Set aside.
• In a large bowl, using an electric mixer on a medium speed (stand or hand mixer), beat together the butter and sugar until pale and creamy.
• Add the eggs one at a time, beating on low each time until just combined. Scrape around the bowl as necessary. Add the milk and vanilla and mix on low. The mix may look curdled, but it will come together once you add the flour.
• On a low speed, add ¼ of the flour mixture at a time until it is all just combined. Careful not to overmix, or your cake will be dense and not fluffy.
• Pour the cake mix into the lamington tin and gently spread, then bake for 20-25 minutes or until a toothpick inserted comes out clean.
• Let it cool completely.
• Once cooled, place a wire rack on top and flip the whole cake over. Remove the baking paper, place another rack on top of the cake and flip again to get it back up the right way.

Icing

• Once the cake has cooled, using an electric mixer, beat the icing sugar, butter and half of the milk together.
• Add more milk until it reaches the desired consistency (you want a nice thick icing), and add the food colouring. Continue to beat for 3 - 5 minutes until light and fluffy.
• Spread it over the cooled cake and add sprinkles.