Squeeze mushrooms of excess water and trim off tough stalks. Cut mushroom caps into quarters. Combine them with the chicken and marinade with the ginger juice, oyster sauce, soy sauces, sugar, salt, pepper, and sesame oil. Set aside 30 minutes.
Wash rice in several changes of water until water runs clear. Drain and add the water. Bring rice to the boil and cook until most of the liquid has been absorbed.
Add the marinated chicken to the rice, burying it in the rice. Drizzle any remaining marinade over the rice. Cover pan with a tight-fitting lid and leave to cook on low heat for 30 minutes. Do NOT lift the lid off the pan. After 30 minutes, remove lid and fluff rice up with a fork and test the chicken to make sure it is cooked all the way through.
Serve rice hot, garnished with spring onion, and fried shallots. (Optional) serve with a small side dish of finely sliced bird chillies seasoned with light soy sauce and a squeeze of lime juice.