A big part of the Big Mac's appeal is the tasty "secret" spread slathered onto both decks of the world's most popular double-decker hamburger. So what's so special about this sauce? It's basically just thousand island dressing, right? Pretty much. But this sauce has a bit more sweet pickle relish in it than a typical thousand island salad slather. Also, I found that this clone comes close to the original with the inclusion of French dressing. It's an important ingredient—ketchup just won't do it. That, along with a sweet-and-sour flavor combo from vinegar and sugar, makes this sauce go well on any of your home burger creations, whether they're Big Mac clones or not. If you like this recipe, check out Todd Wilbur's McDonald's Special Burger Sauce.

Source: Even More Top Secret Recipes by Todd Wilbur.