Balsamic Marinated Pork Loin

1 1-pound boneless pork loin
½ cup balsamic vinegar
2 shallots, chopped 
2 teaspoons minced garlic (about 4 cloves)
2 teaspoons dry mustard

Remove any visible fat from pork. Combine vinegar, shallots, garlic, and mustard in a bowl. Place pork in the bowl, cover, and refrigerate for 1 to 2 hours, turning pork occasionally to marinate all sides.
Preheat oven to 375°F. Remove pork from marinade (reserve), and place in a skillet over medium heat. Brown on all sides.
Transfer pork to a casserole pan, and bake for about 15 to 20 minutes, until juices run clear and meat is white in center. While pork is cooking, pour reserved marinade into a saucepan, and simmer over medium-low heat until reduced by half. Serve marinade as sauce to accompany pork.
Makes 4 servings.