Mix chicken with ginger-garlic, spices, lemon and salt. Rest 10-15 minutes.
Pan-fry in a lightly oiled pan until golden and cooked through. Transfer to a bowl.
Add onion, chillies and half the coriander to the chicken.
Whisk yogurt with garlic, salt and sugar until smooth.
Heat mustard oil until smoking, turn off the heat, add turmeric, chilli powder and fenugreek.
Pour hot tadka into the yogurt, swirling gently.
Spoon the yogurt mixture over the chicken, mix gently and finish with remaining coriander.
