Step 1: Make the Secret Sauce

In a small bowl, stir together the mayo, ketchup, Dijon, pickle juice, paprika, and garlic powder until creamy and smooth. Pop it in the fridge while you prep the rest—it tastes even better chilled!

Step 2: Caramelize the Onions

Heat olive oil in a large skillet over medium-low. Add sliced onions and cook slowly, stirring every so often, for about 25–30 minutes until soft and golden brown. If they stick, add a splash of water and keep the heat gentle. Set aside when done.

Step 3: Shape and Cook the Patties

In a bowl, mix the ground beef with salt, pepper, and Worcestershire. Form into 4 thin, oval-shaped patties that match the bread. Increase heat to medium and cook patties in the same skillet for 3–4 minutes per side until nicely browned. Set aside. Drain grease from the skillet, but no need to wash—you want that flavor!

Step 4: Assemble the Sandwiches

Butter one side of each slice of rye bread. On the unbuttered side, layer in this order: Swiss cheese, beef patty, caramelized onions, generous spoonful of secret sauce, cheddar cheese. Top with another slice of bread, buttered side out.

Step 5: Toast the Patty Melts

Wipe out the skillet if needed, then heat it over medium. Cook sandwiches 1–2 minutes per side, pressing gently with a spatula, until the bread is golden and crispy and cheese is gloriously melty.