Masuzushi / pressed salmon sushi wrapped with bamboo leaves

A specialty of Toyama, my hometown prefecture, this pressed sushi with masu salmon is wrapped in bamboo leaves and comes in a magewappa round wooden container. It has also been a favorite ekiben (lit. train station bento) of Toyama since 1912, and is a popular souvenir with tourists and business travelers. Masuzushi is traditionally made with sakura masu (Oncorhynchus masou) that come back to the main river running through the prefecture to the Sea of Japan, and more than a dozen long-established masuzushi specialty shops are found near the river off the city center even today. Each shop's masuzushi has slightly different characteristics, and many locals have their favorite shop. Salmon is first treated with salt and then sugar and vinegar, and finally assembled with sushi rice and bamboo leaves. Yet the sushi is not ready for consumption at this point, as it must be pressed for hours to achieve the delicate blend of taste, aroma and texture.

The recipe below is my most successful attempt so far to recreate the masuzushi from a shop I like in Toyama. I use a stainless flour sifter and pie mold bottom as a magewappa substitute, and dried bamboo leaves for chimaki zongzi as a substitute for fresh bamboo leaves.

Whole recipe: 
1,139 calories; 58.5 g protein; 10.4 g fat; 187.0 g carbohydrate; 185.5 g net carbs; 354 mg sodium (with shiokoji salted rice malt for sushi rice; 674 mg with kosher salt for sushi rice); 99 mg cholesterol; 1.5 g fiber

1/4 of recipe:
285 calories; 14.6 g protein; 2.6 g fat; 46.7 g carbohydrate; 46.3 g net carbs; 88 mg sodium (with shiokoji salted rice malt for sushi rice; 169 mg with kosher salt for sushi rice); 25 mg cholesterol; 0.4 g fiber


<Ingredients>
For masuzushi pressed salmon sushi

(Makes 1 18cm round sushi; serves 4)
Sumeshi sushi rice made with 1.5 cups (270 cc) rice
Approx. 200 g sake no sujime salmon treated with salt and vinegar (below)
10-14 bamboo leaves (not in photo)
1-2 tbsp rice vinegar (to boil dry bamboo leaves; not in photo)

For sake no sujime (salmon treated with salt and vinegar)

Approx. 250-300 g sashimi-grade or commercially frozen wild-caught salmon (see Notes; 280 g king salmon with skin in photo)
3/4 tsp salt (to sprinkle on salmon; 2 g kosher salt in photo)
Sweetened vinegar
     150 cc rice vinegar
     1 1/2 tbsp sugar
200 cc rice vinegar (to rinse salted salmon slices)

<Directions>
1.

First prepare salmon.
Skin & debone, and sogigiri slice salmon at a slant.

Sprinkle salt, and let sit 30-60 minutes.

2.

Meanwhile, in a shallow container, prepare sweetened vinegar (add sugar to rice vinegar, and mix well).

3.

When ready to proceed, rinse salted salmon by dipping salmon slices in plain rice vinegar, and put in sweetened vinegar.

Cover, and let sit for 1+ hours.

4.
In the meantime, cook rice for sushi rice.

5.

While cooking rice for sumeshi, prepare bamboo leaves.
Cut leaves into a suitable length (diameter of mold + several centimeters) to wrap sushi.

Bring plenty of water to boil, add vinegar, and boil bamboo leaves for 1-2 minutes. 

Remove from heat, and keep in water.

6.

When ready to assemble, towel dry each bamboo leaf.
In a mold, put plastic film wrap, and radially lay bamboo leaves. 

Place a weight such as a cup in the center to hold down leaves.

7.
Prepare sushi rice (mix rice and sushi vinegar).

8.

Put sushi rice. 

Make sure to spread evenly, especially around the edge.
Press down with spatula.

9.

Quickly put salmon slices on paper towel to absorb dripping sweetened vinegar, and lay on top of sushi rice.

(Approx. 4/5 of salmon slices are used here.)

10.

Fold down bamboo leaves.

Top with cover (pie mold bottom in photo).

Place weight (cast iron pot with rocks inside), and let sit overnight (12 hours at least) in a cool location.

11.

When ready to eat, remove from mold.

Unwrap bamboo leaves, and cut in triangular fan shape.

Serve as is (no soy sauce or wasabi or any other condiment is typically served with this sushi).

(Myoga Japanese ginger leaf is used as a kaishiki liner in photo.)

<Notes>

• Sushi rice needs to be warm when put in the mold. Have everything (salmon and mold with bamboo leaves) ready before mixing sushi vinegar into hot steamed rice!
• Salmon prep (through salting or marinating in sweetened vinegar) can be done ahead of time, even one day in advance. When using fatty species such as king salmon, marinating it longer in sweetened vinegar helps to eliminate the greasy taste.
• This sushi is eaten at room temperature or slightly cooler.
• If using wild-caught salmon, buy a commercially frozen fillet as a precaution against anisakis, a parasite that is said to die when frozen below -20 C (-4 F) for an extended time (24 hours to 7 days; suggested period varies by source), a condition impossible to achieve with a home freezer. Another advantage of using a hard-frozen fillet is that it is easy to slice thinly when semi-thawed. 
• If you prefer a slightly sweeter taste, add more sugar (1 tsp or 1 1/2 tsp) to salmon marinade.
• Leftover marinated salmon can be used for other dishes such as temarizushi sushi balls and salad.
• Dried bamboo leaves are available at Chinese and Asian grocery stores. In Japan, bright green frozen bamboo leaves can be purchased.
• Among nutrition values, figures other than sodium do not include rice vinegar and sugar absorbed during salmon prep. The sodium figure would significantly increase when using store-bought sushi vinegar or due to the type of salt used for sushi rice prep. (The sumeshi above uses homemade sushi vinegar made of shiokoji salted rice malt.)
• Going back in time, masuzushi's original form is listed as a regional narezushi fermented rice and fish dish in Engishiki, a 10th century book about laws and customs. By the 18th century, a quick version using the vinegar of today was developed.
• Masuzushi is not typically made at home and is something you would buy as a special deli-type meal or as a souvenir.