Preheat the oven to 180°C and grease a cake tin or line it with baking paper.
Mix the cake flour, Milo powder, sugar, baking powder, and salt together in a large bowl.
In a separate bowl, whisk the eggs, milk, oil, and vanilla essence until combined.
Add the wet ingredients to the dry ingredients and mix until smooth.
Slowly add the boiling water while stirring. The batter will become thinner, which helps create a moist cake.
Pour the batter into the prepared cake tin and bake for 30–40 minutes, or until a skewer inserted into the centre comes out clean.
Allow the cake to cool before adding icing.
To make the icing, mix the icing sugar, Milo powder, butter, vanilla essence, and milk together until smooth. Spread over the cooled cake.