How to Make It
Preheat the oven to 450°. In a large enameled cast-iron casserole, heat 1 tablespoon of the olive oil. Add the pancetta and cook over moderate heat, stirring occasionally, until golden, about 5 minutes. Using a slotted spoon, transfer the pancetta to a paper towel–lined plate.
Rub the chicken with the remaining 2 tablespoons of olive oil and season with salt and pepper. Add half of the chicken to the casserole, skin side down, along with half each of the garlic, thyme sprigs and rosemary. Cook over moderately high heat, turning, until golden brown all over, about 5 minutes. Transfer the chicken to a large plate. Repeat with the remaining chicken, garlic, thyme and rosemary. Return all of the chicken and aromatics to the casserole.
Roast the chicken until the breasts are just cooked through, about 15 minutes. Transfer the breasts to a platter. Roast the chicken legs for 10 minutes longer, until cooked through. Add the chicken legs and garlic to the platter; discard the herb sprigs and garlic skins.
Pour off all of the fat from the casserole. Add the white wine, olives and pancetta and cook over moderately high heat, scraping up the browned bits on the bottom, until the wine is reduced by half, 2 to 3 minutes. Whisk in the butter and season with salt and pepper. Spoon the sauce over the chicken and top with arugula, chopped thyme and fleur de sel.