In a small bowl, combine the softened butter, minced garlic, chopped rosemary, chopped thyme, chopped parsley, 1 tsp salt, and 1/2 tsp black pepper. Mix well until everything is evenly incorporated.

Pat the whole chicken dry thoroughly with paper towels. This is crucial for crispy skin. Place the chicken in a large roasting pan or on a cutting board.

Gently separate the skin from the breast and thigh meat using your fingers, being careful not to tear the skin. Take about half of the prepared herb butter and spread it evenly under the skin over the breast and thigh meat.

Rub the remaining herb butter all over the exterior of the chicken, ensuring an even coating. Drizzle the olive oil over the chicken and season generously with 1/2 tsp salt and 1/4 tsp black pepper.

Stuff the cavity with the halved lemon, quartered onion, and 4 sprigs of fresh thyme. Optionally, truss the chicken with kitchen twine for more even cooking.

Preheat your oven to 400°F (200°C). If using a roasting pan with a rack, place the chicken on the rack. If not, place it directly in the pan.

Roast the chicken for 60-75 minutes, or until a meat thermometer inserted into the thickest part of the thigh (without touching bone) reads 165°F (74°C). The skin should be deeply golden brown and crispy. If the skin browns too quickly, loosely tent the chicken with foil.

Once cooked, remove the chicken from the oven, transfer it to a cutting board, and tent loosely with foil. Let it rest for 10-15 minutes before carving. This allows the juices to redistribute, resulting in a more tender and moist chicken.

Carve the chicken and serve immediately with your favorite sides.