Only a few years ago, the Isle of Arran Distillery was (in)famous for its vast range of cask finished whiskies. As a relatively new distillery, this was a reasonable strategy - their single malts were only so old and cask finishes were a way to embellish younger stock.
Since then, the distillery has significantly pulled back to a core of cask finishes that they believe work best with their spirit. Each expression starts with whisky that has spent at least 8 years in ex-bourbon barrels before it is transferred to ex-wine casks. The finishing period varies significantly, from months to years, as the spirit soaks up new flavors. Thus there isn't a defined 'age' for the whisky - it is adjusted depending on how the spirit is maturing. All of Arran's cask finished whiskies are bottled at 50% ABV without chill filtration.
Arran Port Cask Finish
Nose: a layer of port floating over malt, chocolate raisins, a little vanilla, red berries, a bit of floral soap, mineral/flinty. After adding a few drops of water, there are brighter fruits, fudge-ier port/wine notes, and something purple.
Taste: rather hot throughout, somewhat thin up front, richer wine and oak mid-palate, gets malty at the back - becoming sweeter and woodier with time. After dilution, the heat diminishes a lot, there is more chocolate with integrated oak, the malt gets tucked inside the wine, and a hefty dose of black pepper comes out.
Finish: light port and wood influence, malty
While I really enjoyed this whisky, I feel like its appeal is somewhat circumscribed. The alcoholic heat of the undiluted palate can be rather off-putting, though only a small amount of water is necessary for the spirit to hit its stride. While it may just be that I got a rougher batch (bottled 10/8/10), it felt like this might be better at 48% or even 46%, which would make it much more approachable.
With that said, I think Arran has a good thing going here. The port is present without being dominant, with the oak tannins providing a nice counterpoint to the sweeter wine notes, and the chocolate notes trend towards dark rather than milk, so it's not quite the dessert malt that you might expect. Just make sure to give it a try before buying a bottle to be sure that it's going to jibe with your tastes. As a plus, if you live in Oregon, this whisky is only $49 right now, which makes it a pretty good deal in this day and age.
This makes me look forward to trying the other Arran cask finishes to see how they do with the distillery's malt.