by Jonathan Waxman, A Great American Cook
1 3 1/2- to 4-pound free-range, corn-fed, or naturally raised chicken
Kosher salt and freshly ground black pepper
1/4 cup olive oil, plus more for the chicken
8 medium Yellow Finn potatoes
8 garlic cloves
8 tablespoons (1 stick) unsalted butter, at room temperature
2 6-ounce bags spinach (or 3/4 pound bulk spinach)
Heat the oven to 475 degrees.
Remove the gizzards and any extraneous fat from the chicken. Rinse and pat it dry. Salt and pepper the outside and inside well and rub the chicken with olive oil. Place the bird in a large roasting pan and roast, basting every 5 minutes with the pan juices, for 35 to 40 minutes (about 10 minutes per pound), or until an instant-read thermometer inserted in the thicket part of the thigh registers 165 degrees.
Meanwhile, scrub the potatoes (do not peel) and cut into pieces. Place in a large saucepan of cold water, add 6 of the garlic cloves and salt to taste, and bring to a boil. Reduce the heat and simmer for 25 minutes, or until the potatoes are tender. Drain, reserving 1/2 cup of the cooking water. Return the potatoes and garlic to the pot. Add 6 tablespoons of the butter, the 1/4 cup olive oil, and the reserved potato cooking water. Mash well, using a potato masher. Taste and season with pepper, adding more salt if needed. Cover and keep warm.
Wash the spinach and cut off any large stems. Heat the remaining 2 tablespoons butter in a large skillet over medium-low heat. Add the remaining 2 garlic cloves and cook until lightly browned, about 2 minutes. Discard the garlic, add the spinach to the skillet, and cook, stirring, for 1 to 2 minutes or until wilted. Add a good amount of salt and pepper, turn off the heat, and cover to keep warm.
When the chicken is done, remove it from the oven and let it rest for 10 minutes.
Reheat the potatoes and spinach over low heat if necessary. Carve the chicken and serve with the potatoes and spinach.