Preheat the oven to 180°C (160°C fan-forced). Grease and line two 20cm round cake tins with baking paper.

Mix the dry ingredients. In a large bowl, sift together the flour, cocoa, baking powder, bicarb soda, caster sugar, brown sugar, and salt.

Combine wet ingredients. In a separate jug, whisk together the eggs, milk, vanilla, and oil until smooth.

Bring it together. Pour the wet mixture into the dry ingredients. Mix gently until combined — don’t overmix.

Add boiling water. Slowly pour in the boiling water, stirring until the batter is smooth. (The mixture will be thin — that’s perfect for a moist cake!)

Bake. Divide the batter evenly between the two tins. Bake for 30–35 minutes, or until a skewer inserted into the centre comes out clean.

Cool. Leave cakes in their tins for 10 minutes before turning onto a wire rack to cool completely.

For the frosting: In a medium bowl, beat the butter with an electric mixer until pale and fluffy.

Gradually add icing sugar, beating on low until combined.

Add the milk and continue to beat until smooth and creamy.

Once the cakes are completely cool, spread buttercream over one layer, place the second cake on top, and finish with frosting over the top.