In a bowl, combine chicken with all of the ingredients for the chicken marinade; let marinate for an hour. If you use chicken breasts in this recipe, let it marinate 3 hours for optimal flavor absorption.

Heat oil in a large skillet over medium-high heat. When sizzling, add chicken pieces in batches of two or three, making sure not to crowd the pan. Fry until browned for only 3 minutes on each side. Set aside and keep warm. (You will finish cooking the chicken in the sauce.)

Melt the ghee in the same pan. Cook the onions until soft (about 3 minutes) while scraping up any browned bits stuck on the bottom of the pan. 

Add garlic and ginger and sauté for 1 minute, then add garam masala, cumin, turmeric and coriander. Cook for about 20 seconds while stirring occasionally.

Pour in the tomato puree, chili powders and salt. Let simmer for about 10-15 minutes, stirring occasionally until sauce thickens and becomes a deep brown red color.

Stir the yogurt into the sauce. Add the chicken and its juices back into the pan and cook for an additional 8-10 minutes until chicken is cooked through and the sauce is thick and bubbling. Pour in 1/4 cup of water to thin out the sauce, if needed.

Garnish with cilantro and cashews if desired and serve with fresh, hot basmati rice.