MIX vinegar, Mustard and brown sugar in small saucepan. Cook on medium heat 3 to 5 minutes or until the sauce thickens, stirring occasionally. Remove from heat; keep warm.
SEASON steaks with salt and pepper, if desired. Grill over medium-high heat 6 to 8 minutes per side or until desired doneness.
SPRINKLE steaks with blue cheese and drizzle with balsamic mustard sauce. Top with French’s® Crispy Fried Onions before serving, if desired.