Heat the remaining 2 tablespoons olive oil in a large nonreactive skillet. Season the chicken breasts on both sides with salt and pepper and add half the breasts to the skillet, skin sides down. Cook over moderately high heat, turning once, until well browned, about 5 minutes. Transfer to a plate and repeat the process with the remaining breasts. Pour off the fat from the skillet. Return all the chicken to the skillet, lower the heat to moderate, cover and cook until opaque throughout, about 5 minutes longer. Transfer the chicken to a large plate and keep warm.