Preheat the oven to 325°. Season the duck legs with salt and pepper. In a large enameled cast-iron casserole, heat the oil. Add the onion, fennel, garlic and bay leaf and cook over moderate heat, stirring, until the vegetables are softened and just starting to brown, 10 minutes. Add 1 teaspoon of the marjoram and cook until fragrant, 1 minute. Add 1 cup of the wine and 2 cups of the chicken stock and bring just to a simmer. Nestle the duck legs in the casserole, skin side up, and add additional stock if necessary to cover by two-thirds. Cover the casserole and braise the duck in the oven for 1 1/2 hours, until tender.