BBQ sauce
BBQ sauce appears in 7 of the 123 recipes on Burgerman, roughly 6% of the library. In these builds it is what most people actually taste first, and small changes to it move a recipe more than the patty does. You will find it in KFC Smoky Mountain BBQ Sandwich (Copycat), Ribwich (The Simpsons) and Copycat Red Robin Whiskey River BBQ Burger with Onion Straws, among others. The highest-scoring recipe using it is KFC Smoky Mountain BBQ Sandwich (Copycat) at 8.5 out of 10. It turns up most often alongside salt, paprika, black pepper.
