Both of the ways you mentioned sound absolutely horrible. 22 pounds of chocolate wouldn't be a quick death, but it'd be one hell of a painful death. As for the mushrooms, I don't know if you mean normal shitake mushrooms, or those of the magic variety. The shitakes probably wouldn't be as fun as you imagine, and while I love the magic ones, eating one's weight in them would be a terrible terrible terrible experience times a billion.
OT: I would want to have a hemmorhagic stroke in the left hemisphere of my brain, causing my logical faculties to shut down while the right side of my brain slowly is overwhelmed by the beauty of all being before I just fade out. It's a nice, peaceful, enlightening death.