1. Heat a large nonstick skillet over medium-high heat. Coat pan with cooking spray. Sprinkle both sides of steaks with salt and pepper. Add steaks to pan; cook 3 1/2 minutes on each side or until desired degree of doneness. Remove steaks from pan; cover and keep warm.
2. Add port and shallots to pan. Cook 1 minute or until liquid almost evaporates, scraping pan to loosen browned bits. Stir in broth; cook until reduced to 1/3 cup (about 1 minute). Remove from heat; stir in mustard. Serve steaks with sauce.
Port, a fortified dessert wine, has a distinctively smooth sweetness. If you don't have port, substitute red wine.