If you ever find yourself in the lush and mountainous Toyama Prefecture, you must get your hands on a round of Masu sushi. This giant piece of pressed sushi is the perfect combination of seasoned trout and rice.
Masu sushi originated around the Edo period and is a kind of pressed sushi. It is similar to oshizushi, which is popular in Osaka. It consists of pieces of salted trout and seasoned with vinegar, pressed on a bed of rice. This pressing process allows the rice to absorb some of the delicate flavors of the trout.
Masu sushi is quite popular in Toyama prefecture, so you can find many restaurants serving it while enjoying slightly different flavors at each restaurant. You can also buy masu sushi as ekiben at JR Toyama Station.
Unlike Tokyo-style nigiri-zushi, the sushi is not raw, so you do not have to refrigerate it. That being said, it needs to stay at roughly 20°C (around 68°F). It will last up to three days, so while you do not have to eat it right away, you should eat it soon.
Masu sushi is kept in a round wooden box called mage-wappa. The box is sealed tightly with two bamboo sticks and inside, the sushi is pressed between bamboo leaves.
Traditionally, people use cherry trout from the Jinzu River in Toyama City for masu-zushi. However, the population of cherry trout has dwindled, so instead they use ones from Hokkaido or even import them.
Cherry trout is not all that common, even in Japan, but it tastes very similar to salmon.
One of the great things about this kind of sushi is that it is not very strong tasting. This means it will likely please even those who are more averse to fishy food. It is strikingly different from kabura-zushi, commonly eaten in Ishikawa and Toyama prefectures, which has a quite strong fermented smell.
Masu sushi comes as one giant round of sushi. You need to cut it into small sections as you eat it, or wedges if you are sharing. If you buy it as an ekiben, a plastic knife will come in the bento box.
The flavor of salted trout and rice is excellent, and you will definitely realize why this is so popular.