# What You Need:
→ Patties
01 - 1 pound ground beef (80/20 blend)
02 - 1 teaspoon Worcestershire sauce
03 - 1/2 teaspoon garlic powder
04 - 1/2 teaspoon kosher salt
05 - 1/4 teaspoon freshly ground black pepper
→ Onions
06 - 2 large yellow onions, thinly sliced
07 - 2 tablespoons unsalted butter
08 - 1/4 teaspoon salt
→ Assembly
09 - 8 slices rye bread
10 - 8 slices Swiss cheese
11 - 4 tablespoons unsalted butter, softened
12 - Optional: 2 tablespoons mayonnaise
# Steps:
01 - In a mixing bowl, combine ground beef, Worcestershire sauce, garlic powder, salt, and pepper. Form into 4 equal patties slightly larger than bread slices.
02 - Heat cast iron skillet over medium heat. Add 2 tablespoons butter, onions, and salt. Cook, stirring occasionally, until golden and caramelized, about 12 to 15 minutes. Remove onions and set aside.
03 - Increase heat to medium-high. Place patties in skillet and cook 3 to 4 minutes per side until browned and cooked through. Remove and set aside.
04 - Wipe skillet clean. Butter one side of each bread slice. Place 4 slices, buttered side down, in skillet. Layer each with a slice of Swiss cheese, a beef patty, caramelized onions, another slice of Swiss cheese, then top with second bread slice, buttered side up.
05 - Cook over medium heat until bread is golden brown and cheese melts, about 3 minutes per side. Press gently with spatula to form an even crust.
06 - Slice each sandwich in half and serve immediately while hot.
