Pour off all but 2 tablespoons of the fat in the casserole. Add the onion, smashed garlic cloves, raisins and chopped walnuts to the casserole and cook over moderate heat, stirring occasionally, until the onion is softened and golden brown, about 7 minutes. Add the saffron water, chicken broth, pomegranate juice, cardamom, allspice, dried lime and cinnamon stick and bring to a boil over moderately high heat. Return the chicken pieces to the casserole, skin side up, along with any accumulated juices. Cover and braise the chicken in the oven for about 35 minutes, until the breasts are cooked through.