Oh. Well... Never Mind.

My thanks to my friend Penny, who sent the mushroom photo in my previous post to an expert, Russ Cohen. He subsequently dashed my hopes, telling me it's merely Leucoagaricus leucothites or Lepiota naucina. At least its description says it's an uncommon species, and also this:

Edible but best avoided due to possible confusion with poisonous species.  

You bet. You can read what Mr. Cohen says in his comment on my previous post. Thank you, Mr. C.!

Our resident mycologist, crossy-pawed as usual, and a tad smug.

Possum claims he knew it was Lepiota Naucina all along, but didn't want to rain on my fungal parade. Whatever. He and the rest of this household do know at least one or two things about fungus — microsporum canis — after all.