Preheat oven to 400 degrees F. Trim any excess skin or fat from chicken. Sprinkle chicken with pepper and salt. In a 12-inch cast-iron or other heavy oven-going skillet heat oil over medium-high heat. Add chicken, skin side down; cook about 3 minutes or until lightly browned. Turn chicken; sprinkle with snipped sage.
Place skillet in oven. Roast for 15 minutes. Carefully add shallots and 1/4 cup of the broth to skillet. Roast for 15 to 20 minutes more or until chicken is no longer pink (170 degrees F). Remove chicken and shallots from skillet; cover and keep warm.
For sauce, add the remaining 1/2 cup broth and the wine to skillet. Bring to boiling; reduce heat. Boil gently, uncovered, for 2 to 3 minutes or until reduced by about half. Remove from heat.
Transfer chicken to dinner plates. Return shallots and any collected juices to skillet; add butter, mustard, and sage leaves. Cook and stir until butter is melted. Immediately spoon sauce over chicken.