Patty Melt with Secret Sauce

In a small bowl, mix together the mayonnaise, Dijon mustard, barbecue sauce, and hot sauce until smooth.

In a large mixing bowl, combine the ground beef, Worcestershire sauce, salt, and black pepper. Mix gently just until incorporated.

Divide the beef mixture evenly and form into 6 oval-shaped patties of similar thickness.

Melt the butter in a skillet over medium heat. Add the sliced onions and cook, stirring occasionally, until the onions are soft and golden brown.

Heat a separate skillet over medium-high heat. Cook the beef patties for 2 minutes per side, until browned but still juicy. Remove patties and wipe the skillet clean.

Spread a thin layer of butter on the outer sides of each slice of bread.

Place buttered bread slices, buttered side down, on the skillet. Top with 1 tablespoon of secret sauce, 3 tablespoons of caramelized onions, a slice of cheese, a beef patty, a second slice of cheese, more onions and secret sauce, then top with another bread slice, buttered side up.

Cook sandwiches on both sides over medium heat until the bread is golden brown and the cheese is melted. Repeat with remaining sandwiches.