Trim the root of the shimeji mushrooms and separate them. Cut the shiitake mushrooms into thin slices and shred the stems.

In a pot, combine rice, water, dashi granules, and soy sauce. Heat over medium heat until boiling, stirring gently with a wooden spatula. Add the mushrooms and bring to a boil again, then reduce to very low heat and cover with a lid slightly ajar. Simmer for 30 minutes.

Once the desired consistency is reached, add salt and gently mix to adjust the flavor. Pour in the beaten egg, cover, and turn off the heat. Let it steam for 1-2 minutes.