Wash the rice thoroughly (at least 5 times). Drain well in a sieve.
In a pot, combine the rice, water, kelp, white part of the spring onions, and mushrooms. Let it soak for 1 hour.
After 1 hour, remove the kelp.
With the lid open, cook over medium heat for 5 minutes, stirring occasionally.
Reduce to the lowest heat, cover with the lid, and cook for 12 minutes. (If you smell anything burning around the 10-minute mark, turn off the heat immediately.)
Remove from heat and let it steam for 15 minutes. Never open the lid during this time.