Clean chicken chunks and pat-dry those.
Now make a paste of 2 Onions.
Marinade Chicken with Onion paste, half of the Ginger and garlic paste, and half of Turmeric Powder, Red Chili powder, Cumin powder, Coriander powder, sugar, and salt.
Add 1 tablespoon Mustard oil and 100g Yogurt/ Curd to the marinade as well.
Mix properly.
Keep the chicken in the refrigerator for at least four hours.
While cooking, roughly chop the remaining onion.
Heat 4 tablespoon Mustard Oil in a deep-bottom pan.
Temper the oil with Bay leaf, Dry Red Chilli, Black and green cardamom, and also with Cinnamon stick.
While the tempering emits an aroma, add the remaining sugar and let it caramelize.
Now add chopped onion and fry till it turns light pink.
Do not over-fry the onion else the gravy will turn bitter.
Once fried, add the remaining ginger and garlic paste and fry for a minute.
Now add the remaining curd and cook on a slow flame till the oil leaves the edges.
Meanwhile, with the remaining spices except garam masala (Turmeric Powder, Red Chili powder, Cumin powder, Coriander powder, sugar, and salt), along with 1 tablespoon Mustard oil, make a thick paste.
Add this spice paste to the pan and cook for 2 minutes.
Now add the marinated chicken along with the marinade.
Mix thoroughly on low flame.
Now cook for 20 minutes on a low flame and stir continuously.
Stirring is the key to making the perfect Chicken Kosha.
The chicken will release sufficient moisture while cooking, which will be enough to cook the chicken.
There is no need to add extra water.
Once done, add Shahi Garam Masala to it.
After 20 minutes, the chicken will be properly cooked, the gravy will be semi-dry, and it will leave oil on the edges.
You must check for consistency.
Kosha Mangsho is not a dish served with excess runny gravy.
Serve Chicken Kosha hot with your choice of Paratha, bread, roti, Pulao, or rice.