Coprinus comatus, a.k.a. the Shaggy Mane
One characteristic of Coprinuses is that they deliquesce, that is, they decay by melting into ink rather quickly. And by quickly I mean a few hours sometimes, so the window of opportunity to find these guys, cook, and eat them is fairly short. Once a mushroom begins to decay, it's inedible, just like other foods; rotten is no good! Anyway, as soon as I picked these Coprinuses, I brought them home, cut them in half, made some tempura batter, and set about frying them in bacon grease.
They were interesting. They didn't really have any flavor, or perhaps a delicate one that got overpowered by the tempura/bacon grease. The texture was fasinating though. They were kinda slimy and stringy, but firm and tender at the same time. It had sort of a calamari-like quality to it. One cookbook describes them as "not slimy like okra, but delicious like octopus" - That's pretty much it. I want to try sauteing them next time.