Wipe both sides of konbu seaweed using a tightly squeezed and damp cloth. Rinse dried mushrooms briefly in water.
Hydrate the konbu in 600 ml water, and dried mushrooms in plenty of water to soak. Do so in separate bowls as you chill them in the fridge for 1 to 2 hours.
When it's done, put the konbu with the soaking water, 3 tablespoons of water from the shiitake mushrooms and slowly boil over medium heat.
Remove the konbu right before it comes to a boil. Turn the heat to high and simmer to reduce for about 3 minutes to rid of any chlorine odor.
Add bonito flakes. When it comes to a boil again, turn the heat off and scoop out a fair amount of the floating bonito flakes. The tip when using bonito flakes for soup stock is not to reduce it too much.
Strain through parchment paper and that's the golden soup stock.
Add 500 ml of the golden soup stock into a pot over heat. When it starts to boil, turn the heat down and add thinly sliced dried shiitake mushrooms.
Add light-colored soy sauce and salt to season. Done Dish it up, and serve with green onion toppings if you wish.
Story Behind this Recipe
I was craving a super-simple osuimono clear soup. Since this is easy to make, I took careful steps to prepare the stock The mushrooms are so juicy when bitten into and are absolutely irresistible.
Please adjust the amount of salt to your liking Also good to add tofu. I recommend Japanese dried shiitake mushrooms! You can really tell the difference of its umami-rich flavor.