Step 1

Stir the yogurt and tandoori masala powder together in a large bowl until thoroughly combined; add the chicken and toss to coat evenly. Marinate in refrigerator for 1 hour. Drain and discard any excess marinade.

Step 2

Puree the onion, ginger, and garlic with the water in a blender until it forms a smooth paste; set aside.

Step 3

Heat 1 tablespoon oil in a large skillet over medium heat. Cook the chicken in the hot oil until lightly browned on all sides, about 5 minutes. Remove from skillet and set aside. Heat the remaining 2 tablespoons in the skillet. Fry the onion paste in the hot oil until the moisture is mostly evaporated, about 3 minutes. Sprinkle the garam masala and chili powder over the mixture; cook 1 minute more. Pour the tomato sauce into the mixture, reduce heat to medium-low, and cook another 5 minutes. Return the chicken to the pan along with the half and half; bring to a boil. Add the butter, fenugreek leaves, and salt; reduce heat to low and simmer uncovered until the chicken pieces are no longer pink in the middle, 15 to 20 minutes.