Halve the chicken, with the breastbone, backbone and the first two digits (tips) of the wings removed.
Season the chicken halves on both sides with salt and freshly ground white pepper. Set a 12" cast iron skillet over high heat and when it is hot, add the olive oil. Swirl the skillet to coat it evenly, and then lay the seasoned chicken halves, skin-side down, in the skillet. Sear until golden, about 3 minutes.
Transfer the skillet to the oven and roast until the chicken is nearly cooked through and the skin is crispy, about 17 minutes. Turn the chicken over and continue to roast, skin-side up, until it is cooked through -- 3 to 5 minutes.
While the chicken is roasting, combine the butter with the garlic and thyme in a small bowl, and stir well to blend.
As soon as the chicken is removed from the oven, spread the garlic butter over the skin and serve immediately.