"Double Cask" refers to a method of aging spirits, particularly whiskey, in two different types of barrels. The first cask is typically made of American oak, which imparts flavors like vanilla and caramel. After a period of aging, the spirit is transferred to a second cask, often made of European oak or previously used for sherry, which adds complexity and depth to the flavor profile. This technique allows distillers to create a more nuanced and layered taste experience. The combination of different wood types and previous contents of the casks enhances the final product, making it more appealing to whiskey enthusiasts.