Editor’s note: The theme of Gohan Lab is to help people make simple, tasty “gohan” (meals).

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The last in the series on the art of freezing focuses on “chirashi-zushi,” literally sushi with various ingredients that are “scattered” throughout.

Such sushi that requires several simmered ingredients may not be a daily fare, but if you cook more than you need when you have time, the leftovers can be frozen and used later in various arranged versions.

For easier preparation, the ingredients were limited to three. The amount of dashi stock listed in the recipe may seem small, but there is no need to worry since the fresh shiitake mushroom will release water. The carrot will also soften in about five minutes.

A point to note when mixing the vinegared rice with the ingredients is the temperature of the rice. Unless it is piping hot, the rice will not absorb the liquid sufficiently and turn out watery. The use of freshly cooked rice is preferable, but if cooked rice that has been kept warm in the rice cooker is used, heat it a little in the microwave.

The “kinshi-tamago,” egg cooked in thin layers and cut into fine strips, that tops the rice can also be frozen. Mitsuba leaves and dried “nori” laver are equally tasty alternatives to the snow pea. If pouches of sweet simmered thin fried tofu are filled with vinegared rice mixed with the ingredients, you will get “inari-zushi.”

REMOVE AIR TO PREVENT OXIDIZATION

Cooking expert Akiko Watanabe gave us some tips on freezing. Firstly, freeze the food in amounts that can be used up at a time. Refreezing should be avoided because the flavor will deteriorate.

To prevent oxidization, remove air by pressing down when wrapping the food in plastic wrap. Warm food should be cooled before wrapping, laid in a flat aluminum container and placed in the freezer. Since aluminum is high in thermal conductivity, the food will freeze quickly. When thawing in room temperature, the food will defrost faster when sandwiched between flat aluminum containers.

Freeze vegetables, meat and fish in separate places in the freezer and write down the content and date of freezing on the storage bags with an oil-based marker.

BASIC COOKING METHOD

(Supervised by Akiko Watanabe in the cooking aspect and Kazuhito Kajiwara in the cookery science aspect)

* Ingredients (Serve two)

[4 batches of ingredients for chirashi-zushi for two servings]

180 grams carrot, 8 fresh shiitake mushrooms, 3 (100 grams) small “chikuwa” fish paste, 1 and 1/4 cups dashi stock

[To make two servings of chirashi-zushi]

320 grams (1 “go” when cooked) piping-hot rice, 1 batch of ingredients for chirashi-zushi, some fine strips of cooked egg, 6 snow peas boiled and cut into fine strips

About 379 kcal and 2.5 grams salt per portion

1. [To make ingredients for chirashi-zushi]

Peel carrot and cut into 3-cm fine strips. Cut off stem from shiitake mushrooms and slice finely. Cut chikuwa in half lengthwise and slice finely.

2. Add dashi stock, carrot and shiitake in pot and place on medium heat. Place lid and cook for about 5 minutes. Add chikuwa, 1 and 1/3 Tbsp sugar, 2 Tbsp soy sauce and reduce while mixing occasionally (PHOTO A). Turn off heat when liquid is mostly gone.

3. Spread in flat container to cool. Separate into four equal parts and wrap each in plastic wrap (PHOTO B). Lay in flat container and freeze. When frozen, place in freezing storage bag.

4. [To make chirashi-zushi]

Microwave a batch of frozen ingredients at 600 W for 2 minutes to thaw.

5. Add sushi vinegar (mixture of 2 Tbsp vinegar, 2 tsp sugar, 1/2 tsp salt) to piping-hot rice and mix. While it is still warm, add ingredients for chirashi-zushi and mix (PHOTO C). Cool by using hand fan or other tool. Top with egg strips and snow pea.

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Akiko Watanabe is a cooking expert specializing in Japanese cuisine.

Kazuhito Kajiwara is a former professor at the Tokyo University of Technology who specializes in the study of food preservation.

ARRANGED VERSION

Simmered “hijiki” seaweed (Serves two)

Thaw 1 batch of the ingredients for chirashi-zushi. Briefly rinse 20 grams dried hijiki and immerse in generous amount of water and reconstitute until it is no longer hard. Drain on sieve and cut roughly into length of 4 to 5 cm. Heat 2 tsp oil in frying pan and cook hijiki. When it is coated with oil, add 1/4 cup water, 1 and 1/2 tsp sugar, 2 tsp soy sauce, the ingredients for chirashi-zushi and simmer on medium heat while mixing occasionally until almost no liquid remains.

COOKERY SCIENCE

When food is kept in the freezer for a long time, the frozen water content will turn into moisture and the food will dehydrate. The food will also oxidize and take on the smell inside the freezer. This is a condition called freezer burn when the food has been damaged. To prevent freezer burn as much as possible, the food should be wrapped tightly to minimize exposure to air, placed in a storage bag and used within a few weeks.

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From The Asahi Shimbun’s Gohan Lab column