Cook the noodles in a large saucepan of boiling water for 5 minutes or according to the packet instructions until just tender.
Meanwhile, heat the oil in a saucepan, add the spring onions and garlic and fry gently for 1 minute. Add the chilli, ginger, black bean sauce and stock and bring to the boil. Stir in the pak choi or spring greens, soy sauce, sugar and peanuts, then reduce the heat and simmer gently for 4 minutes.
Drain the noodles, rinse with fresh hot water and spoon into 4 warmed soup bowls. Ladle the soup over the top and serve immediately.