Cook rice in salted boiling water until tender, about 20 minutes. Drain and set aside.
Combine all marinade ingredients and marinate kingklip and prawns for about 30 minutes. Meanwhile, fry onions in a little oil in a very deep frying pan or wok until golden, 5–10 minutes. Add peppers and fry a further 10 minutes, add mushrooms and fry a further 5 minutes. Remove from pan and set aside.