Sprinkle both sides of steaks with 1 1/2 teaspoons of the seasoning. Grill steaks on the rack of an uncovered grill directly over medium coals to desired doneness, turning once halfway through cooking time. (Allow 9 to 11 minutes for medium rare and 11 to 13 minutes for medium.) Transfer steaks to a serving platter.
Meanwhile, in a small bowl combine sour cream, mustard, chives, and remaining seasoning. Spoon sour cream mixture on top of steaks. Serve any leftover sour cream mixture on baked or mashed potatoes. Makes 4 servings.