Ingredients
1 lb ground beef
1 large onion, thinly sliced
8 slices rye bread
4 slices Swiss cheese
4 slices cheddar cheese
Butter, for grilling
Salt and pepper, to taste
1/2 cup mayonnaise
2 tablespoons ketchup
1 tablespoon sweet pickle relish
1 teaspoon Worcestershire sauce
Directions
Start by making the secret sauce. In a small bowl, combine mayonnaise, ketchup, sweet pickle relish, and Worcestershire sauce. Mix well and set aside.
In a large skillet, melt 1 tablespoon of butter over medium heat. Add the sliced onions and cook, stirring occasionally, until they are caramelized, about 15-20 minutes. Remove from the skillet and set aside.
Divide the ground beef into 4 equal portions and shape them into thin patties. Season both sides with salt and pepper.
In the same skillet, cook the patties over medium-high heat until they are cooked throug