In a microwave-safe 1-quart casserole combine undrained chili with beans, barbecue sauce, and mustard.
Make 4 small slits crosswise in each frankfurter, cutting to, but not through, the opposite side. Stir into bean mixture in the casserole.
Cover and micro-cook on 100 percent power (high) for 4 to 5 minutes or until mixture is heated through and frankfurters curl, stirring once. Place curled frankfurters on hamburger buns or uncurl and place on hot dog buns. Spoon chili mixture atop. Makes 4 servings.