For marinade: In a dish or bowl, blend cornflour with rice wine; stir in lemon juice, soy sauce, chillies, ginger and garlic. Blend and stir in chicken pieces to coat. Cover and refrigerate to marinate for 3 to 4 hours.
In a wok or large frying pan, toast the sesame seeds over medium heat, shaking the pan until the seeds are a golden brown colour. Remove seeds and set aside.
To same wok or frying pan, add sesame oil and vegetable oil and heat slowly.
Drain chicken, reserving marinade, and stir-fry in wok a few pieces at a time, until browned. Remove chicken with a slotted spoon and set aside.
Add mushrooms and green capscium to same wok or frying pan and stir-fry for 2 to 3 minutes. Add the spring onions and stir-fry 1 minute more.
Return chicken to pan, together with reserved marinade, and stir over medium high heat for another 2 to 4 minutes, or until the ingredients are evenly coated with the sauce. Sprinkle toasted sesame seeds on top and serve immediately.