Make the Sauce

• In a small bowl, combine the mayonnaise, ketchup, grated onion, pickle relish, and smoked paprika. Whisk until smooth. Set aside.

Caramelize the Onions

• Melt 2 tablespoons of butter in a large nonstick skillet over medium-high heat. Add the sliced onions and cook, stirring every few minutes, until they’re golden brown and softened—this will take about 10 to 15 minutes. For deeper caramelization, let them cook longer, stirring occasionally. Transfer the onions to a plate and cover to keep warm.

Prepare and Cook the Patties

• In a mixing bowl, combine the ground beef, Worcestershire sauce, salt, pepper, and garlic powder. Gently mix until just combined. Divide the mixture into four equal portions and shape into oval or round patties that will fit your bread slices.
• Wipe out the skillet if needed, then preheat it over medium heat. Cook the patties for 3 to 4 minutes on each side until they are golden brown and fully cooked.

Assemble the Patty Melts

• Spread a generous tablespoon of the prepared sauce on each slice of bread. Top each slice with a slice of Swiss cheese. On four of the slices, add a cooked patty and a portion of the caramelized onions. Finish by topping with the remaining bread slices, sauce-side in, to form sandwiches.

Grill the Sandwiches

• Butter the top slice of each sandwich. Put the sandwiches in the skillet with the buttered side down over medium-low heat. Butter the top side while the bottom browns. Cook until the bread is golden and crispy and the cheese starts to melt, about 3-4 minutes. Flip carefully and brown the other side. For even melting, cover the skillet loosely with foil as they cook.

Serve

• Serve warm straight from the skillet while the bread is crispy and the cheese is deliciously melted. Add pickles on the side if you like!