In a large glass measuring cup or bowl mix together the coconut milk, greek yogurt and cream. Stir in the tomato paste, garlic, ginger and all the spices. Mix well.
Spray the inside of your crockpot bowl with cooking spray or grease with olive oil. To the bowl sprinkle the onion over the bottom. Add the chicken and then pour the coconut milk mixture over the chicken so the chicken is completely covered. Add the butter and place the lid on the crockpot. Cook on high for 4 hours or on low for 6 to 8 hours. Stir once or twice during cooking, but it is not necessary.
When ready to serve taste and season with salt and pepper if desired. Serve over rice with a big piece of fresh Naan.