Generously butter the inside of two 1.2 litre/2 pint pudding basins.
Spoon half the golden syrup into the base of each pudding basin and set aside.
Beat the butter, sugar and cocoa powder together in a mixer until fluffy.
Beat in half the eggs followed by half the flour and when well combined, add the remaining eggs and flour. The mixture should be at just dropping consistency. Add a splash of milk if the mixture is too thick.
Spoon the mixture into the pudding basins only filling them three quarters full, then smooth the top with the back of a spoon.
Loosely cover with cling film, allowing room for the cling film to inflate as the mixture rises, and cook in the microwave on high power for five minutes. The pudding is done when a skewer inserted into the centre of the pudding come out clean.
Leave to stand for five minutes then run a blunt knife around the edge of the pudding to loosen the sides, carefully invert onto a deep plate and remove the basin.
Cut the puddings into 8 generous wedges each and serve with custard.