12 slices Swiss cheese (or American cheese if you prefer)
1 large onion, thinly sliced
3 tbsp butter, divided
For the Secret Sauce:
½ cup mayonnaise
2 tbsp ketchup
2 tsp Dijon mustard
1 tsp pickle relish
Dash of hot sauce (optional)
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Instructions:
1. In a bowl, mix ground beef with Worcestershire sauce, salt, and pepper. Shape into 6 thin patties.
2. Heat 1 tbsp butter in a skillet, cook onions low and slow until caramelized (about 15 minutes). Set aside.
3. Cook beef patties in the same skillet until browned and cooked through.
4. Mix all sauce ingredients in a small bowl and set aside.
5. To assemble: Spread secret sauce on one side of each bread slice. Layer with cheese, a beef patty, caramelized onions, another slice of cheese, then top with bread.
6. Melt butter in skillet, grill each sandwich until bread is golden and cheese is melty.
