That's just wrong. America has many fungi Italy doesn't. I don't think the copper penny idea is a good one. I have heard another wife's tail about adding silver to cooking mushrooms. That one doesn't work with our Amanita mushrooms either, and probably wouldn't work with the equally deadly Galerina mushrooms either.
Keep in mind: ALL mushrooms are edible ... once. Even the deadly poisonous kind, or the ones that encourage you to get a liver transplant immediately.
Some mushrooms are edible more than once. I prefer those myself.
And one final caveat: some people like Alexander H. Smith are allergic to all mushrooms. It happens. But Smith loved mushrooms so much he devoted his life to their study. He'd bring the good ones home to try on his wife and daughter.<G> Nancy seems fine, the last time I spoke to her. But Alexander also stated in his mushroom field guides that Gyromitra esculenta was edible. Uh, check the second paragraph again. Gyromitrin poisoning is cumulative. You can have a meal or two within a week, and not seem to suffer to ill consequences. But a third meal the same week might kill you. Nancy has stated it's best just not to eat any Gyromitras. She's still alive. Word to the wise.