Pour hot water over dried shiitake mushrooms and let it soak for few hours.
In a bigger pot, on a medium-low heat fry celery root (chopped in a tiny cubes), chopped carrot, and garlic.
Add shiitake mushrooms (including the water they were soaking in). Pour in water or vegetable broth and add salt. Simmer for 2-3h, until stock will get darker. At the end add miso paste and mix it together.
Ready stock drain through strainer. Prepare the ramen pasta and other toppings.