Arctic Circle food chain claims to have invented "fry sauce'in 1948. However, their sauce recipe is a very guarded secret. Some say fry sauce is really just Thousand Island dressing, renamed. Fry sauce should be smooth. At one point Utah was the "fry sauce" state. I know that when I ask for "fry sauce" in any other state east of Colorado, I am looked at very funny. Other fast food restaraunts like Carls Jr, Hires, Big H, Apollo Burger, and The Training Table offer their own variation on the popular sauce. Up until 1999 Utah's McDonalds franchised offerred the fry sauce.
version 1: 1/3 cup ketchup/2/3 cup mayonnaise
version 2: 1/4 cup ranch dressing
1/4 cup chili sauce
1/4 tsp garlic powder
dash of liquid smoke
1Version 1: mix catsup and mayonnaise till thoroughly blended, serve with french fries.
Mix completely and serve with hot French fries.
Tastes great on hamburgers too.
3A couple more interesting variations: bargeque sauce rather than catsup, buttermilk to thin mixture, add various seasoning salts, add a little horseradish mustard, or what ever comes to mind.