To prepare the filling heat oil in a wok or frying pan and fry ginger, garlic and spring onions for 30 seconds then add mushrooms. Stir fry on high heat until mushrooms are just cooked. Remove mushrooms from wok and wipe clean.
Beat 2 of the eggs in a bowl. 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 slightly soft, place one quarter of the mushrooms and one quarter of the 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.