Нет, похоже...
Butterbeer was a real drink, the earliest reference to buttered beer is from The Good Huswifes Handmaide for the Kitchin, published in London in 1588, made from beer, sugar, eggs, nutmeg, cloves and butter back in Tudor times. Another old recipe for buttered beer, published by Robert May in 1664 from his recipe book The Accomplisht Cook, calls for liquorice root and aniseed to be added.

http://www.medievalcookery.com/recipes/butterbeer.html