Not seen these before but apparently are quite common.
Looks like shaggy inkcap (Coprinus comatus). Fun fact: after it's picked it turns into black goo very quickly!
Gotta cook those bad boys within a few hours, otherwise they start to ink up (not the best not the worst, still edible). Some people even let them completely turn into goo for specific recipes.
I know little about fungi, it is a pretty picture, never the less.