In a small bowl, soak cashews in very hot water for 10 minutes. Drain and add to the bowl of a food processor; set aside.
In a medium bowl, place chicken pieces and sprinkle with turmeric and 1 teaspoons garam masala. Pour in lime juice and coat; set aside for 30 minutes.
In a large saucepan over medium heat, add 1 ½ tablespoons ghee. When hot, add onions and sprinkle generously with ground sea salt; sauté until caramelized, about 25 minutes. Using a slotted spoon, transfer to a bowl to cool off.
In the bowl of a food processor, add garlic to the cashews as well as green and red chilies, ginger, caramelized onions and ¼ cup chicken broth. Process until the mixture resembles a thick paste; set aside.
In the same saucepan over medium heat, add 1 tablespoons ghee and when hot, working in batches, fry the chicken (thighs skin side down at first) just enough to brown on both sides, about 3 to 4 minutes per side; transfer to a plate.
Return the saucepan on medium heat and when hot, add cardamom pods, whole cloves, bay leaves, and cinnamon stick; sauté for 1 ½ minutes.
Add the onion paste, remaining 1 teaspoons garam masala, brown sugar, cumin, coriander, paprika, salt and freshly ground black pepper. Pour in remaining ¾ cup chicken broth; stir, Add chicken back (thighs skin side up), cover, reduce heat to medium-low and cook for 15 minutes.
When time is up, add sour cream and stir gently to combine. Spoon sauce over chicken pieces and pour in heavy cream; stir once again. Simmer until heated through, about 7 to 10 minutes.
When ready, garnish with chopped cashews and cilantro and serve with white rice and naan bread.