Cook rice following the absorption method on the packet. Drain. Spread over a baking tray, separating the rice garins with a fork. Cool to room temperature. Cover and refrigerate for 2 hours or until cold (see note).
Combine the kecap manis, soy sauce and sweet chilli sauce in a jug. Heat a wok over high heat until hot. Add 2 teaspoons of the oil and swirl to coat the wok surface. Add the egg and swirl to form a thin omelette. Cook for 30 seconds or until egg sets. Slide omelette onto a board. Roll up and thinly slice crossways.
Heat the remaining oil in wok over high heat. Add the onion, garlic and mushrooms. Stir-fry for 2 minutes or until mushrooms are tender. Add the chicken. Stir-fry for 1–2 minutes or until sealed. Add the prawns. Stir-fry for 2 minutes or until prawns turn pink.
Add the rice, green onions, cabbage and soy mixture to the wok. Stir-fry for 4-5 minutes or until rice is heated through. Stir in the sliced omelette. Sprinkle with shallots and chopped chilli, if desired. Serve.