This is a lichen, the mushroom being the way in which the fungal partner in the lichen produces spores. On the soil around the mushroom you'd find a green algal film or mat (and there might be a very slight hint of that in one of your photos). The alga is the other partner in the lichen and fungal filaments wrap themselves around the algal cells. The degree of development of the algal mat varies considerably, as you can see if you look at some of the other sightings of this species.