Slice the 400 grams Japanese cucumber thinly (about 1/16-inch thick) and toss them with the ½ teaspoon salt to coat evenly. Let this rest for at least 20 minutes while you prepare the soup.
400 grams Japanese cucumber, ½ teaspoon salt
Add the 30 grams toasted sesame seeds to a mortar and use a pestle to coarsely grind them.
30 grams toasted sesame seeds
Add the 1 tablespoon evaporated cane sugar and grind it in with the sesame until the mixture looks like damp sand.
1 tablespoon evaporated cane sugar
Add the ⅓ cup miso and grind this into a paste with the other ingredients.
⅓ cup miso
Add about ¼ of the 2 cups dashi stock and combine with the mixture until it's smooth.
2 cups dashi stock
Add the remaining dashi and mix together.
2 cups dashi stock
You can also do this in a blender or food processor by pulsing the toasted sesame seeds and sugar together before adding the miso and all of the dashi and pulsing until it's free of lumps.
To serve the Hiyajiru, massage the salted cucumbers until they release a lot of liquid and turn translucent.
400 grams Japanese cucumber
Use your hands to squeeze out as much water from them as you can and transfer them to a serving bowl.
400 grams Japanese cucumber
Top with the soup, add a few ice cubes and garnish with the 5 leaves green shiso and thin slices of 1 myoga. Serve with Shichimi togarashi for sprinkling to taste.
For the 4 servings cooked short-grain rice, rinse the freshly cooked (or reheated) rice in cold water to chill and remove any excess starch. Then, drain it and serve in rice bowls.