# List of Ingredients:
→ Beef Patties
01 - 1 lb ground beef (80/20 blend)
02 - 1/2 tsp kosher salt
03 - 1/2 tsp freshly ground black pepper
04 - 1/2 tsp Worcestershire sauce
→ Onions
05 - 2 large yellow onions, thinly sliced
06 - 2 tbsp unsalted butter
→ Sandwich Assembly
07 - 8 slices rye bread
08 - 8 slices Swiss cheese
09 - 4 tbsp unsalted butter, softened
# How to Make It:
01 - Melt 2 tablespoons butter in a large cast-iron skillet over medium heat. Add sliced onions and cook, stirring occasionally, until deeply caramelized and golden brown, about 15 to 18 minutes. Remove onions to a bowl and wipe skillet clean.
02 - Combine ground beef, kosher salt, black pepper, and Worcestershire sauce in a medium bowl. Gently mix and shape into 4 oval patties roughly the size of the bread slices.
03 - Heat the skillet over medium-high heat. Add patties and cook for 3 to 4 minutes per side until browned and cooked through. Transfer cooked patties to a plate.
04 - Spread softened butter on one side of each bread slice. On the unbuttered side of 4 slices, layer one slice Swiss cheese, a beef patty, a generous amount of caramelized onions, another slice Swiss cheese, then top with the remaining bread slices, buttered side out.
05 - Place sandwiches in the skillet over medium heat (work in batches if necessary). Cook for 3 to 4 minutes per side, pressing gently, until bread is golden brown and cheese melts.
06 - Allow sandwiches to rest briefly, then slice in half and serve hot.
