If you plan to keep fiddleheads, the best bet is to blanch them, bottle them with the water you blanched with, top up with water, salt then boil the bottles. I can't wait to pick up my bottles while home on vacation to NB in June.
To serve... Bring the fiddleheads to a boil, cover and turn the burner off and serve in about 5 mins or so. Generously drown with butter and add salt, pepper and/or vinegar - as desired. Best served with Atlantic Salmon or speckled trout.