Put the chicken on a board and shred into bite-size pieces using a couple of forks. Return the chicken to the stock with the noodles, sweetcorn, mushrooms, spring onion and soy sauce. Simmer for 3-4 mins until the noodles are tender.
Ladle into two bowls and scatter over the remaining spring onion, mint or basil leaves and chilli, if using. Serve with extra soy sauce.