This is the easiest way to roast a chicken in a pan, in the oven, at home. By breaking your bird down into two pieces and cooking them fast, you'll get crispy, dark, golden-brown skin and super juicy meat, all in under half an hour.
Preheat oven to 500 F, or as high as it will go. Preheat cast-iron skillet over high heat. (Note: Chef Gillespie uses an 8-inch skillet to cook 2 servings; use two 8-inch skillets or one 14-inch skillet to cook 4 servings.) Butcher the chicken: First, make a cut along one side of the backbone, as close to the bone as possible. Carefully cut down until the breast and tenderloin can be pulled away from the carcass in one piece; pop the thigh bone out of the joint, and continue cutting from thigh to wing joint to detach the entire half from the carcass. Repeat procedure with the other side of the chicken. (Reserve the carcass for stock.)
Extend the wing and cut through joint between the flat and the drumette. (Reserve the wing for stock.) Make a cut to separate the breast from the thigh, so you have a leg-and-thigh piece and a breast-and-drumette piece. When the skillet is smoking hot, add the grapeseed oil to coat the bottom of the pan. Pat the chicken pieces completely dry with paper towels; then generously season on all sides with salt.
Very gently lay the leg-thigh in the skillet, skin side down, and cook until the skin is nicely browned, about 2 minutes. No need to peek or move the chicken—just let it cook undisturbed. When the skin is browned, it will release easily from the pan; flip it over so it's skin side up. Add the breast to the skillet, skin side down. Place skillet in the oven and cook, 15 minutes.
After 15 minutes, remove skillet from the oven and check to see if chicken is done: the juices bubbling at the bone should be clear, and the meat should be retracting at the thigh bone. Serve.