Preheat oven to 170C.
Grease, dust, line two 6" round pans or one deep 6" cake tin
In a large bowl mix together flour, cocoa, baking powder, baking soda and salt. Whisk together.
Add the egg, milk, vanilla and oil and beat until combined.
Add the boiling water into the mixture and beat until you get a shiny batter.
Divide the batter equally between the pans.
Bake for 25-35 minutes.
Remove from oven, and let the pan sit on wire rack for 10 minutes.
Now loosen the cakes from the side with a knife and flip on the wire rack.
Remove the baking paper from bottom and allow it to cool completely.