1. Heat a large grill pan over medium-high heat, 3 minutes. Brush both sides of pork chops with oil. Sprinkle both sides with salt and pepper. Cook 4 minutes per side. Transfer to plate. Add onions, garlic, and rosemary to pan; cook 2 minutes. Stir in broth and vinegar; boil 1 minute. Return chops to pan. Reduce heat to low; cover and cook chops 8 minutes, until meat thermometer inserted in center of chops reaches 160 degrees F.
2. Meanwhile, for the Speedy Mashed Potatoes, combine potatoes with chicken broth in 2-quart microwaveproof bowl. Cover with plastic wrap, turning back one corner to vent. Microwave on High 10 to 12 minutes, until potatoes are tender. Add 2 tablespoons butter or olive oil and mash. Season with salt and pepper.
3. Transfer pork chops, onions, and sauce to 4 serving plates. Serve with mashed potatoes. Makes 4 servings.