In a bowl, combine all ingredients and marinate for 1 hour.
In a large pot, heat oil on Medium-High. When hot, add chicken pieces, ensuring not to crowd the pan. Cook for 2-3 minutes a side, until browned. Set aside.
In the same pan, add butter and Onions, and cook until soft and translucent. Add Ginger and Garlic, and sautee for 30-45 seconds. Then add Turmeric, Coriander Powder, Cumin, Garam Masala. Fry until fragrant (15-20 seconds).
Add Tomato Sauce, Ground Red Chili and season with salt to taste. Simmer for 15-20 minutes on low heat, stirring occasionally until Tomato Sauce thickens, and takes on a deep reddish brown colour.
Add Chicken and Heavy Cream, and cook for an additional 10 minutes until mixture is bubbling, glossy, and thick.
Garnish with fresh Coriander and serve with hot Basmati Rice, and/or Naan/Rotis.