Put the mushrooms in a large pan and add the mirin, soy, rice wine vinegar, garlic, ginger, red chilli and pour in the stock.
Simmer for 30 minutes until the mushrooms are tender and the stock is fragrant. Add a little more mirin and soy sauce to season should you wish.
Add the greens and noodles and cook until soft – about 6 minutes. Add the beansprouts and cooked chicken meat and cook for a further 6 minutes.
Divide the chicken, noodles and vegetables between 4 warmed bowls and pour over the stock. Add a few dots of chilli or garlic oil and scatter with spring onions to serve.
Chilli or garlic oil
4 spring onions, finely sliced