Soak the dried shiitake mushrooms in 1 cup hot water. Let this sit while you prepare the rice and prepare the remaining ingredients, for at least 15 minutes. (If you use cold water, soak for at least 40 minutes, preferably longer up to 2 hours.)
Rinse the rice until the water starts to run clear (using a large stainless steel mesh strainer is optional). Drain and put in your rice cooker inner pot or a 3-quartpot. Add 2 ½ cups water and soak for at least 15 minutes. When the rice is done soaking, cook in the soaking liquid in rice cooker until done. (If using a pot, bring water to a boil then reduce heat to low, cover, and cook on low for about15 to 20 minutes, stirring occasionally.)
When you are done preparing the remaining ingredients and started cooking the rice, remove the mushrooms from the soaking liquid, squeeze them to remove excess liquid, and cut off the tough stem. Slice mushrooms into strips. Reserve ½ cup of the soaking liquid; use a strainer to catch any bits of grit or dirt that may have come off the mushrooms.
Heat large saute pan on medium high heat. Add onions and lap cheong to pan and cook until the onions start to become translucent and some of the fat has rendered out of the sausage, about 5 minutes.
Add mushrooms, water chestnuts, mushroom soaking liquid, soy sauce, salt, and sugar to the pan. Stir until well combined and cook until the mushrooms are warmed through.
Add cooked mochi rice, cilantro, and green onions to the pan. If your pan is not big enough to hold all of the rice, mix the rice in a large baking dish or other large bowl (about 5 quarts).
Serve in place of your favorite stuffing or dressing recipe. If using as a stuffing inside of a turkey or other poultry, make sure the poultry is cooked all the way through as the center of the bird might not cook through with the stuffing inside of it.