1. The day before cooking-- Add rice and water to cover into a large bowl. Use your fingers to gently rinse the rice in a swirling motion, then drain the water. Add water to cover the rice with 1” (2 cm) of water. Soak at room temperature overnight. Drain thoroughly before cooking.
2. Heat 1 cup of water in the microwave until hot. Add the dried shiitake mushrooms. Soak until the mushrooms turn soft, 15 to 20 minutes. Once done, squeeze the liquid out of the mushrooms into the soaking water. Slice the mushrooms thinly. Reserve the soaking water for cooking.
3. Cut the rest of the ingredients while rehydrating the mushrooms.
4. Heat the butter in a 4-quart dutch oven (or tight-sealing heavy pot) over medium heat. When the butter has melted, add the shallot and shiitake mushrooms. Cook, stirring frequently, until the onions turn golden and translucent, 6 to 8 minutes.
5. Add the Chinese sausage. Cook and stir for 1 minute. Pour in the Shaoxing wine. Use your spatula to release any brown bits stuck on the bottom of the pan. Cook until the wine has evaporated completely.
6. Add the rice. Stir to mix the rice evenly with the other ingredients. Add the chicken stock and salt. Stir to mix well.
7. Add the water chestnuts. Pour in the soy sauce and dark soy sauce. Gently stir a few times to mix the soy sauce.
8. Cook until the liquid comes to a low simmer. Turn to very low heat and cover the dutch oven. Steam until the rice is cooked through, 20 to 25 minutes. Uncover the pan and taste the rice at the 20-minute mark. If the rice still has a bit of a raw texture, let it cook for another 5 minutes.
9. Once done, uncover the pan and stir with a rice paddle or spatula to fluff the rice. Garnish the stuffing with sliced green onions.