By law Irish whiskey must be subject to maturation for at least three years in wooden casks, such as oak. This leaves some room for experimentation with different types of wood, and Teeling have done just that with this whiskey. Chestnut, which is more porous than oak, is not all that common but I believe that for this expression Teeling have taken the base spirit of their Small Batch whiskey (a malt and grain blend aged between 4 to 6 years in oak) and applied a chestnut finish for 6 to 12 months. Even more, the chestnut casks previously held PX Brandy. An interesting concoction but (for me) ultimately a failed experiment. The chestnut is obvious on the nose, along with some maple syrup as others have noted. The taste carries wood spice but I found it too bitter and sour. Still, it’s good to see them aim for something noteworthy and unique but fall short than try for something blandly popular and succeed.