To make the spice blend: Stir the ingredients together in a small bowl and set aside.
To make the sauce: Melt the butter in a 12-inch nonstick skillet over medium heat. Add the onion and cook, stirring frequently, until the pieces just begin to turn gold, about 5 minutes. Add the garlic, tomato paste and spice blend, and cook for 1 minute, stirring constantly to prevent burning. The spices will be fragrant. Add the tomato sauce and diced tomatoes and stir will. Add the chicken pieces, spoon the sauce over the top and bring to a simmer. Turn the heat to low and cook, uncovered, until the chicken is warmed through and the sauce is flavorful, about 10 minutes. Stir frequently. Remove the chicken to a serving dish and cover to keep warm.
Shake any excess water from the peas. Add the peas and cream to the sauce in the pan, stir well and heat through. Do not boil. Spoon the sauce over the chicken. Serve with rice and warmed pita bread.
Variation: If you prefer shreds of chicken to whole pieces, remove the skin from the chicken and pull the meat into large chunks by hand. Add to the pan along with the garlic, tomato paste and spice blend. Cook for 3 minutes and then add the tomato sauce and continue with the recipe. Serve over basmati rice.