It has been a brutal summer. While much of western Japan has suffered from heavy flooding, the rest of the country has experienced severe heat waves: The city of Kumagaya, located in Saitama Prefecture made headlines for its record breaking temperature of 41.1 degrees Celsius.

While growing up, I spent several summer vacations in Saitama, as my grandfather moved his family and business there from Tokyo back in the 1940s to avoid air raids. Just north of Tokyo, landlocked Saitama tends to get especially hot and humid in the summer, since most of the inhabited areas are located in valleys surrounded by hills or mountains.

As kids, my cousins, sister and I would run around all day in the sun until we had sweated so much that our clothes would be caked with salt. We would down gallons of mugicha (barley tea) and bowls of kakigōri (shaved ice), and my grandmother would urge us to eat one umeboshi (salt-preserved plum) per day. In the evenings, we’d devour watermelons that had been cooled by dangling them in a bucket in the well.

One of the meals my aunt — who was in charge of the large household — often made for us was called hiyajiru (also called hiyashiru), an ice-cold soup made with a base of ground sesame seeds, miso and a little sugar, and then thinned out with cold dashi stock or water.

To this we added thick, homemade udon noodles, mountains of refreshing cucumbers, shiso (perilla) leaves and myōga ginger that had been picked from the garden. It was filling yet refreshing, and somehow I was able to eat tons of it even when I thought I had no appetite.

The first written record of hiyajiru dates back to the Kamakura Period (1185-1333), when a cold soup flavored with miso was thought to have been made by Buddhist priests.

It’s believed that this cold soup was spread across the country by the priests, and eventually became established in regions where the summers were exceptionally hot. There, hiyajiru became a simple, rustic midday meal for farm workers.

Besides being cool and refreshing, the ingredients used in hiyajiru — the vitamin B-rich sesame seeds, the medicinal herbs used as yakumi (toppings), the fermented miso — are thought by some to help combat natsubate, or summer fatigue, too.

Over time, the recipe for hiyajiru used in each region evolved. In southern Miyazaki Prefecture, ground up iriko (dried sardines) or shredded himono (semidried fish) is used as a base, and the miso is toasted before it is combined with the sesame seeds and fish.

In northern Yamagata Prefecture, dried and reconstituted vegetables, tofu, seafood and a handful of fresh vegetables are simmered in a soy sauce-flavored stock before adding cold soup.

The carbohydrate added varies too, depending on the region. Udon noodles have always been traditional in Saitama, where wheat grows better than rice, but in Miyazaki and Yamagata prefectures, cold cooked rice is used more often.

This recipe is for a Saitama-style hiyajiru, to which I have added some himono’ for extra protein. I’ve also used sōmen noodles instead of thick udon to save time cooking.

Hiyajiru: Chilled miso and sesame soup

The key to this dish is to add lots of refreshing toppings, and to chill the soup and the noodles well with ice cubes.

Ingredients (serves 2 to 3):
• 4 tablespoons toasted sesame seeds
• 2 tablespoons awase (blended red and white) miso
• 2 tablespoons mirin or 1 tablespoon sugar
• 1 large or 2 small cucumbers, thinly sliced
• Chilled dashi soup stock or water
• Ice cubes
• Cold noodles (sōmen, udon or hiyamugi) or cold cooked rice

Toppings :
Any or all of the following:
• 6-8 green shiso leaves, shredded
• 5-centimeter piece daikon radish, grated
• 2 myōga ginger buds, julienned
• 1 small piece new young ginger root, julienned or grated
• 1 green onion, chopped
• 1 medium cooked saba (mackerel) or aji himono (semidried horse mackerel), boned and shredded or approx. 1 cup shredded cooked chicken
• Whole toasted sesame seeds

Put the mirin in a small pan and bring to a boil. Let boil for a few seconds to evaporate most of the alcohol, then turn off the heat.
Put the sesame seeds in a large suribachi (mortar).
Crush the sesame seeds using a pestle until they start to becoming a little sticky and oily.
Add the miso and mirin or sugar, and mix well until a paste is formed.
Cook the noodles of your choice.
Slice the cucumber thinly. Shred, grate or julienne the toppings of your choice.

To serve:
Pour about ½ cup (120 milliliters) cold water or pre-made dashi into the grinding bowl, and mix until the paste is dissolved.
Add the cucumbers, about half of the toppings and a handful of ice cubes. Mix well.
Serve the sauce right from the grinding bowl into individual serving bowls, with the cold noodles or rice and the rest of the toppings in separate container, plus a jug of extra dashi or water with ice cubes.
Eat with noodles or rice, more toppings, plus additional dashi or water to taste.

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