smitty will probably reply also, but I have done what you did: blanch, ice water bath, dry on paper towel, froze on cookie sheets, and vac sealed. To reheat them I thawed them in the fridge then yes, sauteed them in a bit of butter with seasoning salt and garlic. Never tried to cook from frozen, unless my memory is wrong on that.
When I visit you, I will bring some smoked venison summer sausage and can help you enjoy a feed of those fiddleheads! 😉
Doug