The shiitake mushrooms are ideal for vegetarian sushi, e.g. shiitake cream cheese maki.
Cover the dried shiitake mushrooms with boiling water and soak for 15 minutes. Alternatively, you can take cold water and soak it for an hour (this should make the aroma of the mushrooms even more intense).
Drain the mushrooms while collecting the soaking water. If necessary remove the hard ends of the handle. If the mushrooms are used for sushi, it is advisable to cut them into strips at this point.
Cover the mushrooms in a saucepan with the soaking water and bring to a boil, then reduce the heat and simmer for 2 minutes. Add the sugar and soy sauce and simmer, stirring occasionally, until the liquid has completely evaporated.
Finally add the mirin while stirring. The last step is not absolutely necessary, but the mirin gives the mushrooms the finishing touches.