Pour off all but 2 tablespoons of fat from the casserole. Add the onions and cook over moderate heat, stirring occasionally, until softened and browned, about 8 minutes. Add the stock, apricots, tamarind and whole black limes and bring to a boil. Return the chicken to the casserole, cover and braise in the oven for about 50 minutes, until the chicken is tender. Transfer the chicken to a platter and tent with foil; discard the black limes. Simmer the sauce over moderately high heat until reduced by one third, about 7 minutes. Stir in the lemon juice, parsley and mint and season with salt; serve with steamed rice.