What is the fine-grained topic of the following text: The Hardknott double imperial stout then replaced the whisky where it was left for six months, giving it chance to absorb all that whisky character - or as Hardknott put it so eloquently on the bottle "enabling the Æther spirit to infiltrate the Blæc magic". Only return the topic.
Ageing Hardknott double imperial stout in a whisky barrel