Mix chicken with ginger-garlic paste, salt, pepper, Kashmiri chili powder, turmeric, and lemon juice. Rest 10-15 minutes.
Brush or spray a pan with very little oil. Pan-fry chicken on medium-high until golden brown. Transfer to a bowl.
Add sliced onion, chopped chilies, and half the coriander to the chicken. Mix well and set aside.
In another bowl, whisk Greek yogurt with garlic paste, salt, and sugar until smooth and creamy.
Heat mustard oil until smoking hot. Turn off the heat and add mustard seeds, fenugreek seeds, turmeric, and paprika.
Pour the hot tadka into the yogurt and swirl gently to keep the streaks.
Pour the yogurt mixture over the chicken mixture. Mix gently.
Finish with more chopped coriander leaves.
Serve with rotis or rice.
