Be sure to thoroughly soak and rinse your fiddleheads, as they can hold a lot of grit in their tight curls. This recipe also works well with asparagus or broccoli and is one of the easiest cream soup bases I have ever used.
Alternatively, pour soup into a blender no more than half full. Cover and hold lid down; pulse a few times before leaving on to blend. Puree in batches until smooth. Return the soup to the pot.