The hard sauce goes on the plum pudding after you've boiled or baked the plum pudding. The pudding itself, if made the old-fashioned way, is hung in a bag where the alcohol works a little wonder. If memory serves me, the suet pudding is made late November and hangs till Christmas...? I think some people pour more alcohol onto the pudding and flame it when serving, and then a boat of hard sauce is passed around and the dinner guests pour on as much sauce as they please--depending upon, I suppose, how sauced they are!