Combine first 6 ingredients in a small saucepan; bring to a boil. Reduce heat to medium. Cook, uncovered, 10 minutes. Set aside.
Place a 12-inch cast iron skillet over medium- high heat until very hot.
Rub both sides of steaks with garlic halves. Spread mustard evenly over both sides of steaks. Sprinkle with Creole seasoning.
Cook steaks 3 to 5 minutes on each side or to desired degree of doneness.
Spoon sauce over steaks.