Season the chicken with salt and pepper. In a large enameled cast-iron casserole, heat the olive oil until shimmering. Add the chicken and brown well over moderate heat, about 10 minutes. Transfer the chicken to a plate. Add the onion and fennel to the casserole and cook over moderate heat, stirring occasionally, until lightly browned, about 10 minutes. Add the garlic and ground spices and cook until fragrant, about 2 minutes.