How to Make It
Preheat the oven to 425°. Season the chicken all over with salt and pepper and place in a large ovenproof skillet along with the head of garlic, cut sides down. Roast for about 1 hour and 15 minutes, until an instant-read thermometer inserted in the thickest part of the chicken breast registers 160°. Transfer the chicken and garlic to a cutting board; let rest for 15 minutes. Pour the pan drippings into a heatproof bowl.
Meanwhile, in the skillet, heat the olive oil. Add the onion, bell pepper, minced garlic and a generous pinch of salt. Cook over moderate heat, stirring occasionally, until softened, about 10 minutes. Add the wine, bay leaf, thyme and the reserved pan drippings. Squeeze the roasted garlic into the sauce and bring to a boil over high heat, then simmer over moderately low heat until slightly reduced, 5 minutes. Discard the bay leaf. Transfer to a blender, add 2 tablespoons of water and puree until very smooth. Season the sauce with salt and pepper.
Carve the chicken and transfer to a platter. Serve with the roasted-garlic pan sauce.