Balsamic glazed Pork Sandwiches

Serves 8. Preheat oven to 450F. LIghtly oil a 9-by-13-inch roasting pan. In a small bowl, mix oregano, coriander, 1 1/2 teapoons salt and 1/2 teaspoon pepper. Rub mixture over port. Place pork in prepared pan. In a small saucepan, bring vinegtar and brown sugar to a boil over high heat. Cook, stirring occasionally, until reduced to 1/2 cup, about 3minutes. Remove from heat. Roast pork 5 minutes; brush with 1/3 of balsamic mixture, coating entirely. Roast another 5 minutes, brush with remaining balsamic mixture. Continue roasting until internal temperature registers 155 degrees, about 10 minutes more. Remove from pan. Let rest 10 minutes; slice 1/4 inch thick. Slice pork just before you're ready to assemble sandwiches. Spread mustard over split rols, then layer half with pork and onions.