Fill a large bowl with hot tap water and place the noodles in it to soak for 20 minutes.
In a small bowl, stir together the fish sauce, lime juice, sugar, oyster sauce, 2 teaspoons of chilli sauce and chicken stock. Set aside.
Heat a wok or large frying pan over high heat and add vegetable oil. When the oil is hot, stir in garlic and cook for about 10 seconds. Add prawns and chicken; cook, stirring constantly until prawns turn opaque and chicken is cooked through, 5 to 7 minutes.
Move everything in the wok out to the sides and pour the eggs in the centre. Cook and stir the eggs until firm. Add the noodles to the wok and pour in the sauce. Cook, stirring constantly, until the noodles are tender. Add a bit more water if needed to finish cooking the noodles. Stir in 200g beansprouts and spring onions. Remove from the heat and garnish with chopped peanuts. Taste for seasoning, adjusting the spice or lime juice if needed.
Serve garnished with fresh coriander and remaining beansprouts and lime wedges on the side.