
Place 3 dry shiitake mushrooms into a bowl of water and put some kind of weight on the mushrooms so that the mushrooms submerge. Leave it refrigerated over night.
The next day, squeeze the soaking water out but save it in a bowl. Place 1/4 cup of the soaking water, sugar, soy sauce and mirin (listed in the 'toppings' ingredients) in a saucepan over medium heat. Slice the shiitake mushroom and put them into the saucepan to simmer for about 20 minutes with otoshibuta (dollop lid).
Let the shiitake mushrooms cool down to room temperature, place them into a storage container and chill in the fridge till the somen noodle is ready to serve.
If you are making kinshi tamago follow this recipe( see note *3)
Make the dipping sauce if you are making mentsuyu from scratch.
Dilute the mentsuyu with water and set aside.
Prepare the garnishes: slice the okura, grate the ginger, thinly slice the myoga, and cut the negi shallots finely.
Boil water (1- 1.5 liters or 6½ cups) in a large pot, add 1 bundle of somen noodle and cook for 2 minutes.
Drain the water and then leave the noodles under the running water to wash and cool down.
Place the noodles in a bowl of ice water to chill.
Serve the noodles with a few ice cubes, the toppings, the garnishes, and the dipping sauce separately.