Heat the butter in a big bowl until melted. Whilst still slightly warm add sugar using an electric mixer beat together thoroughly about 5-10 mins.

Then sieve the cocoa powder into the butter/sugar mixture and again beat until creamy. Add the vanilla and beat it some more. Now add eggs one at a time, beating well after each addition to make sure it's well incorporated.

Remove the mixer and slowly sieve the flour and baking powder into the mixture a little at a time, mixing with spatula or spoon alternate with adding the warm milk as well and stir. Once everything is done pour the batter into a greased 8" pan and bake for 15-20 mins.