To prepare the filling heat oil in a wok or frying pan and fry the ginger, garlic and spring onions for 30 seconds then add the mushrooms. Stir fry on high heat until mushrooms are just cooked. Remove mushroom mix from wok and wipe it clean.
Beat two of the eggs in a bowl and season. Reheat the wok or frying pan and add the oil. When the oil is hot, add the beaten eggs and swirl to spread. When the base is cooked, and the top is till slightly soft, place one quarter of the mushroom mix on half of the omelette, top with bean sprouts and fold over. Remove from the wok. Repeat with remaining eggs making a total of 4 omelettes.
Serve drizzled with the sauce and topped with coriander leaves and chilli.