Place the chicken pieces on a cutting board with flesh-side up. Score deeply at 1-inch intervals with a sharp knife. Pat dry and place in a large rimmed non-reactive baking dish. MARINADE: Combine cumin, paprika, coriander, turmeric and cayenne in a small bowl and mix well. Set aside 3 tablespoons of spice mixture (for Step 10). Combine remaining 6 tablespoons of spice mixture, 8 cloves garlic, 2 tablespoons ginger, yogurt, 1/2 cup lemon juice and 1/4 cup salt in a large bowl and whisk to combine (or process all in food processor). Pour marinade all over chicken pieces, using hands to coat every surface. Cover loosely and refrigerate. Refrigerate and allow to marinate for at least 4 hours and up to 8 hours, turning occasionally. SAUCE: Meanwhile, heat ghee or butter in a large Dutch oven over medium-high heat until melted and foaming subsides. In clean food processor, pulse garlic to yield 4 tablespoons (or crush in a garlic press). Remove excess of garlic from food processor and add about 2 inches fresh gingerroot cut in small chunks, and pulse until finely grated. Add onions and garlic-ginger mix to the Dutch oven. Cook, stirring frequently, until dark and beginning to char in spots, about 10 minutes. Add reserved spice mixture from Step 3. Cook, stirring frequently, until fragrant, about 30 seconds. Add tomatoes and 1/4 cup chopped cilantro, scraping up any browned bits from bottom of pan with a spoon. Simmer sauce for 15 minutes, then puree using a hand blender or by transferring to a tabletop blender in batches. (If you use a VitaMix, you will not need to allow the sauce to cool off first.) Stir in cream and remaining 1/4 cup lemon juice. Season to taste with salt, then set aside until chicken is cooked. TO COOK ON THE GRILL: Light 1 chimney full of charcoal. When all of the charcoal is lit and covered with gray ash, pour out and spread the coals evenly over half of a coal grate. Set cooking grate in place, cover grill and allow to preheat for 5 minutes. Clean and oil the grilling grate. (I recommend a GrillGrate.). Wipe excess marinade off chicken and place over hot side of grill, flesh-side down. Grill without moving until well charred, 5-7 minutes. Flip chicken and cook until second side is charred, 4-5 minutes. (Chicken will not be completely cooked through, which is okay). Transfer to a cutting board and allow to rest 10 minutes. TO COOK UNDER THE BROILER: Line a broiler pan with heavy duty aluminum foil and preheat the broiler to high with the rack set 6 inches below broiler element. Wipe excess marinade off chicken and place on foil-lined pan, flesh side up. Broil until charred an blackened on surface, about 8 minutes (but if you have a professional oven broiler, it may take much less time). (Chicken will not be completely cooked through, which is okay.) Transfer to a cutting board and allow to rest 10 minutes. FINALE: Remove chicken from bone using a sharp knife and cut into rough bite-sized chunks. Transfer chicken chunks to pot of sauce. Bring to a simmer over medium heat and cook, stirring frequently, until chicken is just cooked through, about 10 minutes. Sprinkle with 1/4 cup chopped cilantro leaves. Serve immediately with rice or grilled naan.