Season the chicken with salt and pepper and cook it in the ghee in a large skillet over medium heat on the skin side to brown it and to render the fat from the skin, about 15 minutes. Turn the chicken over and cook on the bone side for about 5 minutes. Remove the chicken from the pan and reserve.
Pour all but 2 Tbs. of the fat out of the pan and stir in the onion, garlic, chiles, and ginger. Cook over medium heat while stirring frequently until the onion lightly caramelizes, about 15 minutes. Add the curry powder and sauté until fragrant, about 2 minutes.
Add the chicken stock to the pan, scraping up any browned bits, and return the chicken pieces to the pan. Bring to a boil, reduce the heat, and simmer, covered, until the chicken is firm to the touch and cooked through, 20 to 25 minutes. Add the coconut milk, simmer until thickened (3 to 5 minutes), and remove from the heat. Transfer the chicken to shallow serving bowls, spoon the sauce over, and sprinkle with the chopped cashews and cilantro.