"Now then," said Slughorn, returning to the front of the class and inflating his already bulging chest so that the buttons on his waistcoat threatened to burst off, "I've prepared a few potions for you to have a look at, just out of interest, you know. These are the kind of thing you ought to be able to make after completing your N.E.W.T.s. You ought to have heard of "em, even if you haven't made "em yet. Anyone tell me what this one is?"