01 -
Mix together mayonnaise, ketchup, mustard, pickle juice, paprika, and garlic powder in a bowl until smooth. Set aside.
02 -
Heat olive oil in a skillet on medium-low. Add sliced onions and cook until soft and golden brown, about 30 minutes. If they start to dry out or burn, add a little water and lower the heat. Remove from the skillet and set aside.
03 -
In a bowl, mix ground beef, salt, pepper, and Worcestershire sauce. Shape into four thin patties that match your bread's shape.
04 -
Cook patties in a skillet over medium heat until browned on both sides. Remove and set aside. Wipe the skillet clean.
05 -
Spread butter on one side of each bread slice. In the skillet, place a slice of bread butter-side down, then layer on Swiss cheese, a beef patty, onions, secret sauce, cheddar cheese, and another slice of bread butter-side up. Cook on medium heat until the bread is golden brown and the cheese has melted, flipping once. Repeat for all sandwiches.