Clinker polypore, or chaga
The clinker polypore is a crispy conk that is dark brown. People used to make a coffee surrogate from the mushroom by drying and grinding it. They also made tea out of it. In Russia, the mushroom has been used in popular medicine as a treatment for a variety of illnesses from gastric ulcer to cancer.
The clinker polypore, or chaga, is a rot fungus that lives especially on birches, but also on other deciduous trees. It sticks – usually in the autumn – to the spots in the trunk of the tree that have been damaged, but it is also found in the cuts that have been caused by freezing weather. The clinker polypore rots only the living part of the tree; it creates a black conk on the tree. The actual sporophores, or fungi, develop between the bark and the core of the tree only after the tree has died. The clinker polypore is common throughout Finland.