Preheat your oven to 400 F (200 C)
Cut your chicken thighs into roughly equal pieces and transfer to a large bowl. Add to it your spices, sour cream, lemon juice, zest and garlic. Mix everything thoroughly until the chicken is perfectly coated. It is recommended that you let your chicken marinate for at least 1 hour before baking (or grilling)
Transfer your chicken into a baking sheet. Bake in your oven for 20 minutes. If it is sunny where you live, it is highly recommended that you grill your chicken on the BBQ.
While your chicken is baking, grab a large skillet large and warm up on medium heat. Melt your ghee in it and add to it your chopped onion, ginger, coriander seeds, mustard seeds and cumin seeds. Cook for 5 minutes and add your coconut milk and the rest of the spices (paprika, curry powder, ground cardamom pods, garam masala, salt and pepper).
Stir your sauce until your spices are combined and add your tomato paste. Stir again. Lower the heat and let it simmer for 15 minutes (or until the sauce thickens).
By now your chicken should be cooked. Remove from the oven and let it sit for 5 minutes.
Add your chicken to the sauce and gently stir. Turn off the heat and let it cook for 5 minutes in the residual heat.
Serve with some Cauliflower rice.