Bring a large pot of water to a boil (unsalted or salted water - according to your preference).
Add the fiddleheads and cook for 2-3 minutes.
Drain the partially cooked fiddleheads and add them to an ice bath to stop cooking.
Use a slotted spoon or colander to remove the blanched fiddleheads from the basin of ice water.
Transfer into freezer-safe containers or freezer bags.
Label with the contents, date, and instructions.
Freeze for up to 1 year in a deep freezer, or up to 6 months in a small freezer.
When ready to prepare: thaw, and steam for 12 minutes, or boil for 15 minutes before eating.