tomalley

thumb|Japanese kourayaki, or blended crab tomalley and roe baked in its shell

Tomalley is the hepatopancreas (the organ that fulfills the functions of both the liver and the pancreas and is the main organ for storing fat and nutrients) of a crustacean used for culinary purposes. It typically refers to those in lobster or crab. Tomalley found in lobster is also called lobster paste, which can be found in the body cavity, and is soft and green; that found in crab is also called crab fat, crab butter or crab mustard, which is yellow or yellow-green in color. It is considered a delicacy, and may be eaten alone but is often added to sauces for flavour and as a thickening agent.