From the Icelandic Foss Distillery, Börkur Bitter is made with Icelandic birch bark. Currently only available in Iceland, this bitter is based from a neutral grain spirit (potato vodka most likely).
The distillery itself is very young, being created only a few years ago (2010) and they pride themselves on having a very unique product which uses sustainably gathered birch trimmings. The bottle itself even has a birch stick in the spirit itself (much like the worm that can be found is poor quality mescal), which adds a nice touch that only seems a bit like a gimmick.
The flavor reminds me completely on the smell, with the old forest sticks flavor a bit more powerful, and not nearly as much bitterness as I was expecting. A bit of warmth from the alcohol, but not nearly as overpowering as the flavor. The finish is what I assume the finish of eating a decaying leaf would be like.
Overall as you can probably find out I am not a fan of this spirit and am curious to know how it could be used in a cocktail, as I cannot find any recipes that use it, and also have no good ideas on how it could be used. Also making this review in Iceland where I purchased the spirit my selection of mixers is limited, but nothing that I can find worked. The distillery looks to be expanding and exporting some spirits, but I would be surprised if the Börkur bitter ever makes its way out of Iceland.