1 medium onion, finely chopped 1 - 3-pound rabbit, cut into 8 pieces 2 tablespoons vegetable oil 2 tablespoons unsalted butter 1 1/4 cup dry white wine 1 3/4 cups chicken broth (13 3/4 fluid ounces) 1/4 cup Dijon mustard 1 teaspoon cornstarch 2 tablespoons chopped fresh parsley leaves
Pat rabbit pieces dry with paper towels and season with salt and pepper. In a deep large heavy skillet, heat oil over moderate heat until hot but not smoking and brown rabbit pieces on all sides in 2 batches. Transfer rabbit to a large bowl.
Cook onion in skillet with 1 tablespoon butter over moderately low heat, stirring, until softened. Add wine and cook until liquid is reduced by about half. Return rabbit to skillet and add broth. Simmer rabbit, covered, until tender, about 45 minutes.
Transfer rabbit to large bowl. Boil sauce until reduced to about 2 cups. In a small bowl mix together 1/4 cup sauce and mustard and mix mixture into sauce.
In another small bowl stir cornstarch into 1 tablespoon cold water and whisk into sauce. Simmer sauce, whisking, 3 minutes, or until thickened. Whisk in remaining tablespoon butter, parsley, and salt and pepper to taste.
Return rabbit to sauce skillet and cook over moderately low heat, turning rabbit to coat with sauce, until heated through.