Ankimo is the cooked liver of the monkfish, one of the glories of Japanese sea cuisine.
The liver is first soaked in sake and deveined, then rolled up in cloth or saran wrap and steamed until fully cooked. The liver may contain dangerous flukes and so is not eaten raw. Once cooled, the tube of cooked liver is typically sliced into rounds and served with scallions, grated ginger, and ponzu sauce.
As with many Japanese dishes, much of the flavor of the dish comes from the main ingredient rather than added seasonings, so the liver must (of course) be extremely fresh. The sake treatment eases some of the strong flavor of the liver. Monkfish liver recipes in the West do include delicate poachings, but also the full range of liver treatments including heavy fat-laden terrines, of which liverwurst is perhaps the extreme example. The Japanese dish is far more delicate.