1. Heat 1 tablespoon butter in 12-inch nonstick skillet over medium-high heat for an electric stovetop (medium heat for gas). Add onion; cover and cook 10 to 12 minutes, until golden, stirring once. Sprinkle onion with 1/2 teaspoon salt; cook 3 to 4 minutes more, until caramelized. Add broth, vinegar, brown sugar and mustard; bring to boil. Reduce heat slightly and cook 3 minutes. Transfer to bowl; wipe out skillet with paper towels.
2. Sprinkle chops with remaining 1/2 teaspoon salt and pepper. Heat oil in same skillet 1 to 2 minutes over medium-high heat. Add pork and brown 1 minute per side. Cover and cook 5 minutes, then turn chops and cook 5 to 6 minutes more, until an instant-read thermometer inserted 1-1/2 inches deep into side of each chop registers 160 degree F. Spoon onion sauce over pork; cover and cook 1 minute. Dot onion with remaining 2 teaspoons butter. Remove skillet from heat; cover and let stand 2 minutes. Transfer chops to a serving platter. Serve with fettuccine, if desired. Makes 4 servings.