In a large pot, combine the water, kombu, dried shiitake mushrooms, and bonito flakes. Bring to a boil, reduce the heat and allow it to simmer for at least 15 minutes.
The longer you let the stock cook, the stronger the dashi will be. Strain any foam that forms during this process. When the broth is ready, place a mesh strainer over a bowl and strain the broth.
Return the broth to the pot over low heat and slowly introduce the miso. Take a ladle and place the miso in it. Take about half a ladle full of the stock and mix the miso with the stock until it is combined. Keep the broth heated but not simmering.
Risotto
In a small pan, heat the mushrooms over medium-high heat and cook until they have turned slightly golden brown. Remove from the heat and set aside.
Melt butter in a large pan over medium heat. Add the shallot and garlic and cook until the shallots become translucent, about 5 minutes. Add the arborio rice and cook for 2 minutes.
Add the sake and stir in well. Cook until all the sake has been absorbed by the rice.
Add the miso dashi stock in ½ cup increments. Stir until the rice fully absorbs the liquid. Repeat this until all of the liquid is used.
Remove from the heat and stir in the mushrooms and parmesan cheese. Season with salt and pepper.