Oshizushi is any kind of sushi that has been pressed into shape, similar to the way that onigiri rice balls are pressed to form the rice into a hand-holdable mass. When I was in Toyama back in 2016 for the TV show, Yokkaichi’s mother made masuzushi as part of a large festive dinner. Masuzushi is a specialty of Toyama, and it is an oshizushi made in a round press. The press is lined with bamboo leaves and layered with rice and then fresh trout before it is pressed into a solid “cake” of sushi. The masuzushi is then cut into wedges like a regular cake and served. This dish is so iconic to Toyama that you can buy it in the train station as a souvenir.
Anyway, in order to make oshizushi of any kind, you need a press. I have a plastic press for making onigiri, but it is not good for making anything other than the triangular rice balls. The best presses are a kind of bottomless box, with a lid that slides inside like a piston. It does not have to be super-solid since you’re only applying finger pressure, but it should be fairly sturdy. The open bottom enables you to place the box (“hako” or “bako“) onto a sheet of nori or other flat surface, fill it with rice and other tasty stuff, then insert the lid and compress the ingredients into shape. You can then lift the box from the surface and use the lid to push the oshizushi out the bottom.
I made my oshizushihako from some maple I bought at the Alben Sawmill and machine-planed down to 5/8″ thickness. The corner joints are the large-fingered box joints that I see on most medieval Japanese boxes, and since I didn’t want my food to contact glue I secured the joints with copper nails. The piston lid is a flat piece of maple that is roughly 3″ x 4.24″ to follow the 1 by 1.414 ratio that is commonly seen in Japanese woodworking. This is also a good size for making onigirazu “rice sandwiches”.
For best results, use hot freshly cooked rice and wet the box and lid thoroughly to keep the rice from sticking.
