Stir together brown sugar, pepper, salt, onion powder, and paprika in a bowl. Coat pork chops with spice mixture. Cover and place in the refrigerator for 6 hours to overnight.
Preheat the oven broiler. Place an oven rack in the highest position.
Place pork chops onto a slotted, two-piece broiler pan. Stir together maple syrup and spicy mustard in a small bowl.
Broil pork chops in the preheated oven for 5 minutes. Flip, then broil for another 5 minutes. Brush tops with mustard glaze and cook for 1 minute. Flip chops over, brush again, and broil for another minute or until cooked to your desired degree of doneness. Remove pork chops to serving plates and top with additional glaze, if desired.