Put a large pan of salted water on to boil. Peel and finely slice the onion. Halve the pepper, scoop out the seeds and white pith, then finely slice it. Halve any larger mushrooms so they're all roughly the same size. Snap the woody ends off the asparagus spears (bend them and they'll snap in the right place) then chop them into 3cm-long lengths. Peel and grate the garlic and ginger.
Warm a wok or deep frying pan over a high heat for 2 mins. Chop the chicken pieces into small, bite-sized chunks. Add ½ tbsp oil and the chicken to the wok. Stir fry for 8 mins till the chicken is browned all over. Scoop it out of the pan and pop it onto a plate.
Add another ½ tbsp oil to the wok and add the red onion, pepper, button mushrooms and asparagus. Stir fry for 5-8 mins till the veg have started to char and become tender.
Return the chicken to the wok. Stir in the garlic, ginger, 1 tbsp each Thai green curry paste and Worcester sauce and the tamari. Stir fry for 2-3 mins till fragrant.
Pour 150ml boiling water into the wok. Pop on a lid and simmer for 10 mins till the chicken is cooked through.
While the chicken is simmering, cook the noodles. The water in the pan should be boiling. Add the noodles to the pan and simmer for 3-5 mins till the noodles are tender and cooked through.
Drain the noodles and add them to the wok. Toss everything together to mix to coat in the sauce. Divide the Thai chicken noodles between 2 warm plates and serve straight away.