Heat the oil in a large saucepan. Add the chicken and sear the outside, cooking for 3-4 minutes. Add the onion, garlic and ginger and cook, stirring, for 1 minute until fragrant. Add the cumin, coriander and turmeric and cook for a further 1 minute.
Meanwhile, cook the noodles according to the instructions on the packet. Drain and refresh with cold water, then set aside.
Stir in the stock, miso, soy sauce and coconut milk. Cover and bring to a boil. Uncover, reduce the heat to medium and add the pak choi and mushrooms. Simmer for a further 3 minutes, then stir in the noodles until they heat through. Sprinkle over the remaining spring onions and sesame seeds to serve.