Preheat oven to 450°F. Add oil to a large skillet and heat over medium-high heat. Add chicken to skillet, skin side down. Cook undisturbed until the skin browns (about 5 min). Turn and cook 3 min. on the other side.

Place chicken in the oven. Cook 20 min. or until just done. Juices will run clear. Remove the chicken to platter, tent with foil, and keep warm.

Poor cooking juices into glass bowl. Place skillet over medium-high heat and add butter and shallots. Cook, stirring, until they are tender, about 2 min. Add the vinegar and raise heat to high. Cook 2 min., until the powerful smell has subsided. Add juices back to skillet and cook until the mixture is slightly reduced and somewhat thickened, 3 to 5 min. Remove skillet from heat, add 2 tablespoons butter, and swirl until butter is melted. Return the chicken and any accumulated juices to the skillet. Toss the chicken in the sauce and serve!