Black trumpet mushrooms are cornucopia-shaped, with ruffled lips, and a dark brown to dark purplish black in color. They are thin and papery. In spite of their fragile appearance, they have a lot of flavor. They are delicious sauteed in a little butter, and they dry very well. They do very well in soups and risottos and have a very deep flavor.
If you can't find them locally, try one of these online resources.
(Image: Kathryn Hill)