Hirame nigiri is a traditional type of nigiri sushi. It consists of hand-pressed sushi rice that's topped with hirame or olive flounder. Most sushi restaurants serve hirame nigiri from late autumn to the end of winter. The fish has a chewy texture and subtle, mild flavors.
The fish is filleted, the slices are salted, and then placed on top of the rice in order to create this nigiri sushi. Typical accompaniments to the dish include pickled ginger (gari), soy sauce, and wasabi on the side. Interestingly, each fillet has a muscle at the edge, a little flesh on the fin called engawa, which is the most exercised part of the fish and it's more chewy and stronger in flavor than other parts, making it very prized if the fish has been properly filleted.