Melt butter, sugar then add sieved cocoa, add milk. Stir making sure there are no lumps! Bring to the boil and leave bubbling for 1 minute (non stick pan advisable!). Take off heat and stir until cooled, (have been known to put sauce pan in sink of cold water whilst stiring) you will find the mixture eventually becomes nearly fudge like, you want to catch it just when you can dribble the mixture and it keeps a 'shape'! Don't over stir or you will end up with fudge! Hope that all makes sense, well worth it.