Season the chicken with salt and pepper. In a wide Dutch oven (I used a cast-iron skillet for later transfer to oven) over medium-high heat, warm the olive oil. Working in batches, brown the chicken, 2 to 3 minutes per side. Transfer to a plate.
Add the garlic to the pan and cook, stirring, for 1 minute. Remove the pan from the heat. Add the chicken, rosemary, thyme and lemon zest and stir to combine. Cover the pan, transfer to the oven and roast for 20 minutes. Baste the chicken with the accumulated juices. Continue roasting, uncovered, until the chicken is cooked through and the juices run clear when the meat is pierced with a knife, about 30 minutes more.
Transfer the chicken to a platter; leave the garlic in the pan. Cover the chicken loosely with aluminum foil.
Set the pan over medium heat and mash the garlic with the back of the spoon. Add the wine and cook for 3 minutes. Add the stock and cook, stirring occasionally, until slightly thickened, about 5 minutes. Whisk in the butter a few pieces at a time. Season with salt and pepper. Transfer the sauce to a sauceboat. Serve the chicken immediately and pass the sauce alongside.
(I made this a healthier version last night by adding the wine at the same time as the stock and just serving the dish with the whole garlic--minus the sauce and the butter at the end). It looked beautiful and was delicious.