There are literally millions of chicken curry recipes out there.
The key to this one - slow cooking. Found this in the book by Khalid Aziz, titled "Step by Step Guide to Indian Cooking". Modified it a lot, but kept the slow cooking part.
Time: 2-3 hours.
Chicken - 1 pound boneless, skinless, chopped to bite-size pieces
or equivalent (1.5 to 2 pound) with bone
Onion - 1 pound, chopped
Tomatoes - 1 pound, chopped
Turmeric - 1 teaspoon
Black Mustard Seeds - 1 teaspoon
Cumin Seed - 1 teaspoon
Cinnamon Sticks - 2
Coriander Seeds - 0.5 teaspoon
Garam Masala - 1 teaspoon
Ginger - 4 tablespoons
Garlic - 4 tablespoons
Red Chilli Powder - as needed
Oil - around one-fourth cup
Heat Oil, when hot, add black mustard seeds.
Use electric chopper to chop all the onions, leave one cup of onions aside, and then add the chopped onions, with the cumin seeds, to the frying oil once the mustard seeds start popping.
Add 1 cup of onions, roughly cut ginger, and garlic (skin removed) to the electric chopper, and chop this mixture real fine.
Once the frying onions are nearly transparent, add the finely ground onion/ginger/garlic mixture to the frying pan, cook for 5-10 more minutes.
Then add the dry spices - turmeric, garam masala, cinnamon sticks, coriander seeds, chilli powder, all as needed.
Cook for a minute or two, and then add chopped tomatoes.
Cook for 5-10 minutes, all this on medium heat.
Then add the chicken pieces, cook for 3-5 minutes, then lower the heat, add water as much as needed to make the curry, and cook on low heat for 60-90 minutes - more if using chicken on bone (2-3 hours).
1) Add half to one cup of plain yogurt after adding the chicken.
2) Add chopped spinach - during the last 30 minutes of cooking.
3) Add half-stick of butter
4) Add chopped cliantro at end