Cover the steak with the soy sauce, mirin and 1 tsp groundnut oil. Fry the steak in a griddle pan for 2 minutes on each side, then rest it. Heat the stock in a pan, add the ginger, chilli and garlic and simmer gently for 5 minutes before taking out the garlic. cook the noodles, rinse under cold water and drain well. Add the noodles, carrot, chinese leaf and beansprouts to the stock and bring back to a simmer, season with soy sauce. Cook for 2 minutes until the chinese leaf has wilted, and divide between bowls. Slice the beef thinly and put on top. Scatter with coriander and spring onions and serve.