Black-footed polypore, Polyporus badius

Didn't know what these were for a while. They were pliable, and BIG. Underside white and smooth.
Polyporus badius.
These change appearance pretty dramatically over the course of their lives, very young ones are pale grey with a smooth rounded outline, from a distance they look like oyster mushrooms. They turn a dark reddish brown as they mature.