Prepare all the vegetables in advance. When ready to serve, 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, reduce the heat and simmer gently, uncovered, for 4 minutes.
Pile the cooked noodles into four serving bowls. Ladle the soup over the noodles and serve immediately.