Stir together the mustard, brown sugar, lemon juice, Worcestershire, and cayenne in a small bowl.
Position an oven rack 3 to 4 inches from the broiler element and heat the broiler to high. Line the bottom of a broiler pan with foil and replace the perforated top part of the pan. Arrange the pork on the broiler pan and season generously on both sides with salt. Brush about half of the mustard mixture over the top of the chops. Broil until the chops are deeply browned in spots, 6 to 8 minutes. Turn the chops over with tongs, brush with the remaining mustard mixture, and continue to broil until the pork is browned and just cooked through (an instant-read thermometer in the center of a chop should register 145°F), about 5 minutes more. Let rest a few minutes before serving. Sprinkle the better-looking sides of the chops with the parsley, if using, and transfer to serving plates.