Beat the eggs with the milk until blended. Fold in the chopped fiddleheads, leeks, and parsley, and half of the grated cheese. Season with salt to taste. Turn into the partially baked shell and sprinkle on the remaining cheese. Decorate the edge with whole fiddleheads. Bake in a preheated 350° oven for 40 minutes, or until set. Let rest 10 minutes before serving.