- With the rack in the middle position, preheat the oven to 350°F (180°C).
- In a pot, bring the broth to a boil. Add the mushrooms, if desired, and cover. Remove from the heat and set aside.
- In a large, high-sided ovenproof skillet or pot over medium-high heat, brown half of the turkey pieces at a time in 1 tbsp of the butter. Season with salt and pepper. Set aside on a plate.
- In the same skillet, lightly brown the onion and garlic in the remaining butter. Sprinkle in the flour and continue cooking, while stirring, for 1 minute. Add the broth with the mushrooms (if using), wine and cognac. Bring to a boil while whisking. Season with salt and pepper. Add the turkey pieces.
- Transfer to the oven and roast, uncovered, for 1 hour 30 minutes or just until the thigh meat easily comes away from the bone.
- Remove the turkey pieces and set aside on a large plate. Over medium-high heat, reduce the sauce for 10 minutes or until it has thickened and coats the back of a spoon. Adjust the seasoning. Return the turkey pieces to the sauce.
- Meanwhile, in a skillet over medium heat, lightly brown the chestnuts and shallot in the butter. Add the breadcrumbs and continue cooking for 1 minute. Remove from the heat. Add the hazelnuts and parsley. Season with salt and pepper.
- Top the turkey with the chestnut garnish. Return to the oven and roast for 5 minutes. Serve immediately.
Ask your butcher to break down the turkey for you: separate the thighs from the drumsticks, debone the breast, then slice each breast in half. The wings, wing tips and carcass are perfect for making a delicious homemade broth.
Look for vacuum-sealed chestnuts in the nut section of most grocery stores.