This is the sauce formerly used on the Bonus Jack and the Jumbo Jack before 1999. It's still available in packets at some locations.
Ingredients
2tbsp mayonnaise
1tbspketchup
2tspyellow mustard
1tspwhite vinegar
1tspdehydrated onionor 1/2 tsp onion powder
1large dropA1 Steak Sauce
2dropsWorcestershire Sauce
1dropTabasco or Sriracha, or other hot sauceoptional
1/4tspXanthan gumoptional
Instructions
Combine vinegar and onion and allow for spices to rehydrate for 30 minutes.
Combine all remaining ingredients with vinegar mixture except xanthan gum (if using).
Slowly sprinkle xanthan into mixture while stirring constantly to avoid lumps
Allow to sit in the refrigerator for 30 minutes for the flavors to develop
Notes
The xanthan gum is optional and is there to thicken the mixture and provide a familiar fast food texture. It doesn't add any flavor so is fine without it.