Country: The Netherlands.
According to an AI identification system this might be a Fistulina hepatica.
Looking into it, Fistulina hepatica has an asexual state that does resemble what I see here (Article: Confistulina: a rare and little-known state of Fistulina hepatica)
But I am still not sure. Fistulina hepatica prefers to grow in oak and chestnut. Unfortunately I did not pay close attention at whether the tree was an oak tree when I took the picture, and from the small piece of bark visible in the photo it is hard for me to tell.
Here is a close-up of the surface of this fungus:
Thanks! So far I agree, I think it is a beefsteak fungus. It seems to be an asexual "anamorphic" state. Is there a reason why you think that being located at the saw off branch scar would induce abnormal growth? I am curious about what the trigger might be.
Normal brackets are at ninety degrees to the grain of the wood, this isn't possible when growing out of sawn off end grain. It's not something that occurs naturally.
That is an interesting observation. I usually see them growing at 90 degrees but I had never really given this any thought. I will pay more attention to this when I see brackets. Thanks!
It's just an idea, brackets grow normally on fallen trees that are horizontal but I think tree rings are a bit too much for them to compute.