1. Prepare the Chicken: Remove the chicken from the refrigerator 45 to 60 minutes before roasting so it can warm slightly. Remove any giblets from the cavity and pat every part of the chicken completely dry with paper towels. Dry skin is one of the most important secrets to achieving crisp, golden skin. Moisture on the surface creates steam, which prevents proper browning.

2. Preheat the Oven: Heat the oven to 425°F (220°C) with the rack placed in the center position. Starting at a higher temperature helps begin the browning process quickly and develops the beautiful golden skin that is expected in traditional Poulet Rôti au Four.

3. Make the Herb Butter: In a bowl, combine the softened butter, minced garlic, chopped rosemary, chopped parsley, juice from half of the lemon, 1½ teaspoons of salt, and 1 teaspoon of black pepper. Mix until smooth and evenly blended. The butter should be soft enough to spread easily without melting.

4. Season Under the Skin: Carefully loosen the skin over both chicken breasts using your fingers without tearing it. Spread about half of the herb butter directly under the skin. This classic French technique keeps the breast meat juicy and seasons it from the inside rather than only the surface.

5. Coat the Outside: Spread the remaining herb butter evenly over the entire outside of the chicken, making sure every part is lightly coated. Sprinkle the remaining salt and pepper over the skin for even seasoning and better browning.

6. Fill the Cavity: Place the squeezed lemon halves, thyme sprigs, and halved shallots inside the cavity. As the chicken roasts, these ingredients gently perfume the meat without overpowering its natural flavor.

7. Tie the Chicken: Tie the legs together with kitchen twine and tuck the wing tips underneath the body. This helps the chicken cook evenly and keeps the thinner parts from overcooking before the thicker parts are fully done.

8. Roast the Chicken: Pour the chicken stock into the roasting pan and place the chicken breast-side up. Roast for 20 minutes at 425°F (220°C). Reduce the oven temperature to 375°F (190°C) and continue roasting for another 55 to 70 minutes, depending on the size of the chicken. Every 20 minutes, baste the chicken with the pan juices to encourage even browning and rich flavor. The chicken is done when the thickest part of the thigh reaches 165°F (74°C).

9. Rest and Serve: Transfer the chicken to a serving platter and loosely cover it with foil. Allow it to rest for 15 to 20 minutes before carving. During this time, stir the roasting juices together to make a simple natural sauce. Carve the chicken and serve with the pan juices spooned over the meat.