For marinade: In a bowl, mix cornflour with stock (or wine); stir in lemon juice, soy sauce, chillies, ginger and garlic. Blend and stir in chicken strips to coat. Cover and refrigerate to marinate for 3 to 4 hours.
In a large frying pan, toast the til, (sesame seeds) over medium heat, shaking the pan until the seeds are a golden brown colour. Remove seeds and set aside.
To same frying pan, add sesame oil and vegetable oil and heat slowly.
Drain chicken, reserving marinade, and quickly stir-fry in a kadhai, a few pieces at a time, until browned. Remove chicken with a jharni/chhalni (slotted spoon) and set aside.
Add mushrooms and green capsicum to same frying pan and cook for 2 to 3 minutes, stirring constantly. Add the green 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.