In a small bowl, combine the mustard's, honey, 2 teaspoons of olive oil. In a sauté pan add 1 teaspoon of olive oil. Add onion and sauté over medium heat until golden and tender, about 5 minutes. Add garlic and sauté for additional 2 minutes, until fragrant. Transfer onion and garlic to an oven safe dish and add chicken to it. Salt and pepper the tops of chicken. Pour the honey mustard mixture on top of the chicken. Arrange rosemary sprigs around the chicken in the pan. Bake covered at 400 degrees for 20 minutes. Remove cover and baste chicken with the mustard sauce. Continue to cook for an additional 20-30 minutes, or until chicken is browned on top and cooked through.