Sea urchins are marine invertebrates that belong to the phylum Echinodermata, protected by a round, spiny shell called a "test." The edible part is the gonad, sold and eaten as "roe" or "uni."
Uni has a rich, creamy texture and a briny, umami-forward flavor. In Japan it is a prized sushi ingredient, usually eaten raw; it also tops rice dishes or folds into sauces and dips. In Ligurian cooking it is worked into "pesto di ricci" with garlic, parsley, and olive oil, and it appears in pasta and risotto. On the U.S. West Coast, chefs favor serving it raw to showcase its delicate texture.
Good uni should be firm, bright in color, and free of discoloration or off-odors; it deteriorates quickly and should be eaten as fresh as possible.