Preheat and Prepare the Bird: Preheat your oven to 200°C (400°F). Pat the chicken dry all over with kitchen paper — this is essential for crisp skin. You want the surface to feel tacky, not slick. Place the chicken in a large roasting tin or a cast-iron skillet.

Make the Herb Butter: In a small bowl, combine the softened butter, minced garlic, thyme, rosemary, parsley, salt, and pepper. Mash it together with a fork until it forms a fragrant, green-flecked paste. The smell at this point is a promise of what's to come.

Season Under and Over the Skin: Gently slide your fingers under the skin of the chicken breast, loosening it from the flesh without tearing it. Take half the herb butter and push it directly onto the breast meat, spreading it evenly. You'll feel the cool skin lift away. Rub the remaining butter all over the outside of the chicken, covering the legs and wings. The bird should now look glossy and speckled with herbs.

Stuff and Surround: Stuff the cavity of the chicken with the quartered lemon and onion. This will steam from the inside, keeping the meat moist and adding a subtle citrus note. Scatter the carrot and celery chunks around the chicken in the tin. Pour the chicken stock around the vegetables — not over the bird — and drizzle the vegetables with the olive oil.

Roast to Golden Perfection: Place the tin in the preheated oven. Roast for 1 hour and 15 minutes to 1 hour 30 minutes. You'll know it's ready when the skin is a deep, burnished gold and the juices run clear when you pierce the thickest part of the thigh with a skewer. The kitchen will smell of roasted garlic and herbs. If the skin is browning too quickly, tent the chicken loosely with foil for the final 15 minutes.

Rest Before Carving: This is the hardest step. Remove the chicken from the oven and let it rest in the tin for at least 20 minutes. The internal temperature will continue to rise, and the juices will redistribute. You'll hear a gentle sizzle as it settles. Do not skip this — carving immediately will release all those precious juices onto the board, leaving you with dry meat.

Carve and Serve: Transfer the chicken to a carving board. Spoon the roasted vegetables onto a serving platter. Carve the chicken at the table for a truly satisfying presentation. The skin should be so crisp it shatters under the knife, revealing steaming, tender meat beneath.