The first photo of the gills shows it might be pink spored: You could put a fresh mature cap gill side down on a piece of white (or half white half black if you have it) paper for a few hours or more to get a spore print, to see what colour the spores are.
I took the print on dark paper, it appears to be white. I have found several other species but am having a really hard time identifying them. It can be very frustrating.
Exasperating yes totally... ... But hey we're apparently drawn to the glorious mystery that is fungi <grin> I don't know what it is yet, nor whether it is edible or not, but mulch would not affect edibility unless perhaps there is something poisonous in the mulch.
