Place a sieve over a bowl, add rice, and rinse it with water. Repeat this process several times, changing the water each time.
Soak the rinsed rice in dashi stock in a pot for at least 30 minutes.
Place the aburaage in a heatproof bowl and pour boiling water over it to remove excess oil. Remove it from the bowl, and once it has cooled enough to handle, drain off the water.
Cut the aburaage, pork belly, and carrots into small, bite-sized pieces. Trim off the base of the shimeji mushrooms and separate them into individual pieces.
Sprinkle the pork with salt, then sauté it in a pan over medium heat until cooked through.
Combine the seasonings (mirin, salt, and soy sauce) with the rice in the pot. Then, evenly distribute the aburaage, pork belly (including pork fat from the pan), carrots, and shimeji mushrooms on top.
Cover the pot and bring it to a boil. Once boiling, reduce the heat to low and continue cooking for 10 minutes, or slightly longer for larger quantities (11 minutes for 4 servings, 12 minutes for 6 servings).
Turn off the heat and let it steam for 10 minutes with the lid still on.