For dressing, whisk first 4 ingredients until sugar is dissolved.
Ensure the fryer is at 175c. Deep fry the Thick cut chips for 4 minutes 30 seconds shaking the basket halfway through.
Meanwhile, place a skillet coated with cooking spray over medium heat. Add steak; cook until meat reaches desired doneness, approx 5-6 minutes per side. Remove from heat; let stand 5 minutes before slicing.
To serve, divide lettuce, tomato and onion between 2 plates; top with chips, steak and cheese. Drizzle with dressing.