Places
The Three Broomsticks
Madam Rosmerta's pub in Hogsmeade, popular with Hogwarts pupils and known for butterbeer. Harry overhears Fudge, McGonagall, Flitwick and Hagrid discussing Sirius Black there while hidden under the table.
In the books
Harry Potter and the Prisoner of AzkabanChapter: 8
Ron and Hermione return from Hogsmeade and tell Harry about the pub’s Butterbeer.