I took three home with me. I couldn’t find my Mushroom book, was in a hurry, so I trusted my judgment, fried them up in olive oil, and ate them as a side dish. I should have recognized then that they weren’t inky caps, because inky caps exude a black substance when you fry them.
They honestly did not taste that good, rather bland in my opinion. I thought to myself, “Gee, I don’t think I’ll ever pick and eat these again.” (Little did I know the truth of my thought at the time).
Britt Bunyard, the founder, publisher, and editor in chief of the mycology journal Fungi, has tasted a death cap. “Very pleasant and mushroomy,” he told me. “A nice flavor, and then you spit it out.”
“There’s nothing in the taste that tells you what you are eating is about to kill you.”
I'm no expert, but Wikipedia says half of one death cap can kill. For some reason, they don't offer an upper range for what will kill.
That doesn't mean you'll have an OK time eating it in small amounts; it will still make you violently ill and cause damage to your liver.
Before I continue, I want to stress that this is not medical advice or even a personal recommendation. Do not do what I am about to say.
In the case above, the important part is spitting it out. The toxins enter the body via the intestinal walls (which is also why symptoms are fairly delayed), so a taste and spit--and probably some rinsing and even more spitting--will mean that relatively little poison makes it any further than your mouth.
Again, I'm not an expert on mushrooms, medicine, poisons or anything else. All of this is from casual reading from the Internet. Don't eat poison.
I've had a black nightshade berry and I can confirm it tasted like a sweet tomato. I assume the poisonous ones taste similar, if they were bitter then accidental poisonings wouldn't be a big concern.