An Important Note on Fiddleheads: Fiddleheads are one of those fleeting vegetables punctuate the spring in New England. They taste like a cross between asparagus and broccoli and are delightful on their own or in a dish such as this. However, they must be cooked, or they are poisonous. To cook fiddleheads, bring a large pot of salted water to a rolling boil. While the water is boiling, rinse the fiddleheads thoroughly in cold water, removing their slippery, papery coverings. Plunge the fiddleheads into the boiling water and cook for 3 minutes. Drain and rinse again with cold water.