01 -
Mix mayonnaise, ketchup, mustard, pickle juice, paprika, and garlic powder in a bowl until smooth.
02 -
Heat olive oil in skillet over medium-low heat. Cook onions until deep golden brown, about 30 minutes. Add water if needed to prevent burning.
03 -
Mix ground beef with salt, pepper, and worcestershire sauce. Form into four thin, oblong patties to match bread shape. Cook in skillet until browned on both sides.
04 -
Butter bread slices. Layer each sandwich: buttered bread (down), swiss cheese, beef patty, onions, secret sauce, cheddar cheese, buttered bread (up). Cook 1-2 minutes per side until golden brown.