In a large bowl, mix the chicken with chili, turmeric, salt and pepper and let marinate for a minimum of 15 minutes to a maximum of 8 hours
In a large pan or skillet, melt 2 tablespoons butter over medium heat
Add the onions, garlic, Garam masala, ginger, cumin, cayenne, cinnamon, salt, and pepper. Cook until fragrant, approximately three minutes.
Add the tomato sauce and simmer. Add the water and cream, and bring back to a simmer.
Return chicken and bring back to a simmer, cover and cook 10 to 15 minutes.
Stir the last 2 tablespoons of butter, salt and pepper to taste
Serve over long grain rice, like basmati, and with naan