# What You'll Need:
→ For the Patties
01 - 1 lb ground beef (80/20 blend)
02 - 1 tsp Worcestershire sauce
03 - 1/2 tsp garlic powder
04 - 1/2 tsp kosher salt
05 - 1/4 tsp freshly ground black pepper
→ For the Onions
06 - 2 large yellow onions, thinly sliced
07 - 2 tbsp unsalted butter
08 - 1/4 tsp salt
→ For Assembly
09 - 8 slices rye bread
10 - 8 slices Swiss cheese
11 - 4 tbsp unsalted butter, softened
12 - Optional: 2 tbsp mayonnaise
# Steps to Follow:
01 - Mix ground beef, Worcestershire sauce, garlic powder, salt, and pepper until combined. Form into 4 equal patties slightly wider than bread slices.
02 - Heat cast iron skillet over medium heat. Melt 2 tablespoons butter, add sliced onions and salt. Cook, stirring occasionally, until golden brown and caramelized, about 12 to 15 minutes. Remove onions and set aside.
03 - Increase heat to medium-high. Add beef patties to skillet, cooking 3 to 4 minutes per side until browned and cooked through. Remove patties and set aside.
04 - Clean skillet. Butter one side of each bread slice. Place 4 slices buttered side down in skillet. Layer each with Swiss cheese, a beef patty, caramelized onions, another slice of Swiss cheese, then top with remaining bread slices buttered side up.
05 - Cook over medium heat, pressing gently with a spatula, until bread is golden and cheese melts, approximately 3 minutes per side.
06 - Cut each sandwich in half and serve immediately.
