How to Make It
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.
Preheat the broiler. Transfer the duck legs to a rimmed baking sheet. In a small bowl, blend the butter with the flour until smooth.
Strain the braising liquid through a fine sieve set into a fat separator, pressing on the solids. Pour off the fat. Transfer the remaining liquid to a medium saucepan. Add the remaining 1 teaspoon of marjoram and boil the sauce until reduced to 1 1/4 cups. Whisk in the butter paste and simmer over moderately high heat until the sauce is thickened, 2 minutes. Whisk in the remaining 2 tablespoons of wine and season with salt and pepper; keep warm.
Broil the duck 8 inches from the heat for 3 minutes, until the skin is browned. Transfer the duck to plates and serve with the sauce.