You may have heard of peated whiskey but not double peated whiskey. Peat is basically decomposed organic plant matter that has decomposed for 1000 – 5000 years, just like coal. Peat can most famously be found in Scotland with 23 percent of the country covered in it.
Historically, Scots used peat to heat pot stills. When drying the damp malt, which is essential in whisky making, the peat-heated fire brings the smoke into the grains. How long the malt is dried over peat determines the smokiness of the eventual whisky.
Double peated whiskey simply refers to the blend of two different types of peated whiskey, giving a usually sublime tasting whiskey.