Bring your chicken to room temperature before starting. Pat it dry thoroughly using paper towels—this step helps the skin crisp up beautifully. Trim any excess fat or leftover feathers.
In a small bowl, mix your softened butter with crushed garlic cloves, chopped rosemary, lemon zest, salt, and pepper. Blend until smooth. This is the flavor bomb that will transform your chicken from good to unforgettable.
Carefully lift the skin over the chicken breasts and thighs and spread the herb butter underneath using your fingers. Then rub the remaining butter all over the top of the skin. The more even your spread, the better your flavor will be throughout.
Slice your lemon and onion (if using) and place them in the bottom of your roasting pan. Add a few sprigs of rosemary and thyme. Lay your chicken breast-side up on top. Pour in the broth and white wine around the edges.
Preheat your oven to 425°F (220°C). Place the pan in the oven and roast for about 60 to 75 minutes. Baste the chicken with pan juices every 20 minutes to keep it moist and golden. Check that the internal temp hits 165°F (74°C).
Once cooked, take the chicken out and let it rest for at least 15 minutes before carving. This seals in the juices and keeps it tender. While it rests, you can simmer the drippings into a quick pan sauce if you like.