You've asked the right person. Coprinus comatus (aka Shaggy Mane) is one of the most edible of mushrooms, has anti-cancerous elements, and is considered one of the "fool-proof four" for collecting.
Another common name is Inky Cap, because during the 1840-1870 period of pioneer expansion, Inky Caps were allowed to turn to ink, then a little sulphuric acid was added to stabilize the goop, and the pioneers literally made ink from them. One of my gr-gr-grandparents diaries, written with Inky Caps collected in Missouri/Kansas, is still owned by my uncle. While the words are faded after 150 years, it is still a valued family artifact.
Shaggy Mane can fruit in mass, but cannot be preserved that is currently known. That's because the mushroom dissolves itself in a process called "auto-deliquesence". More importantly, it has an extremely powerful anti-cancer element, which has eliminated some cancers within 24 hours.
I enjoy Shaggy Manes in gravy over potatoes myself. Get some Jimmy Dean sausage, sautee until well cooked, add some flour to make a roue of the fat, and add as many Shaggy Manes as you can within 3 hours. Yummy and good for you!
There is a little leeway if you see Shaggy Manes in the right stage of development. By plunging the mushrooms in water containing ice, it is possible to keep the mushrooms from auto–digesting themselves for up to 72 hours. But they are best used immediately.
For more information on the medicinal aspects of Coprinus comatus, I recommend Paul Stamets' "Growing Wild and Medicinal Mushrooms", as well as Christopher Hobbs' "Medicinal Mushrooms". Some excellent medical citations.
