Bring a pot of water to the boil. Cook rice noodles until tender, about 1 minute only. Drain well. Divide the noodles between two serving bowls. Place the Vietnamese mint leaves or other herbs, plus the basil and bean sprouts on top.
In another saucepan, heat the stock, with the Kaffir lime leaves, chillies and ginger. Bring the stock to a boil then reduce the heat to a simmer. Drop the pieces of salmon in and poach quickly for 1 minute until the fish is opaque and cooked through.
To serve, place salmon pieces on top of noodles and herbs. Ladle hot stock mixture into bowls and garnish with the chillies and extra bean sprouts. Serve immediately accompanied with extra chilli and soy sauce.