01 - Combine all marinade ingredients in a large bowl and mix thoroughly. Coat chicken pieces completely with the mixture. Cover and refrigerate for at least 1 hour, preferably overnight for maximum flavor penetration.
02 - Preheat oven grill or grill pan to high heat. Arrange marinated chicken on a foil-lined tray or skewers. Grill for 8 to 10 minutes, turning once, until lightly charred and cooked through. Remove and set aside.
03 - Heat butter and oil in a large skillet over medium heat. Sauté onions for 5 to 6 minutes until golden brown. Add minced garlic and ginger paste, cooking for 1 minute until fragrant.
04 - Add crushed tomatoes, cumin, coriander, paprika, garam masala, sugar, and chili powder. Simmer while stirring for 10 to 12 minutes until the sauce thickens and oil begins to separate on the surface.
05 - Transfer sauce to a blender and purée until completely smooth, or use an immersion blender directly in the pan. Return the blended sauce to the skillet.
06 - Add grilled chicken pieces to the sauce. Stir in heavy cream and kasuri methi. Simmer gently for 8 to 10 minutes until flavors meld and chicken is tender. Season with salt to taste.
07 - Sprinkle chopped fresh cilantro over the dish. Serve immediately with basmati rice or naan bread for a complete meal.