Mix marinade ingredients and rub over chicken, then refrigerate for 30 minutes.
Heat oil to 190°C and deep-fry chicken for five minutes until golden and cooked.
Drain fried chicken on kitchen paper and set aside.
Heat 3 tbsp oil in a pan until smoking, then briefly stir in dried chillies.
Add cumin seeds and garlic, stirring quickly until the garlic changes colour.
Add onions and peppers, stir-frying for two minutes until softened.
Add chicken, salt, sugar, chilli powder, and ground cumin, stir-frying on high for 2 minutes.
Stir in the soy sauce until well mixed.
Add cornflour paste and stir quickly to glaze and thicken the sauce.
Mix in lemon juice and chopped spring onions.
Serve immediately with rice, noodles, or watercress salad.