# What you'll need:
→ Beef
01 - 1.1 lbs ground beef (80/20 blend recommended)
02 - 1/2 tsp salt
03 - 1/2 tsp black pepper
→ Onions
04 - 2 large yellow onions, thinly sliced
05 - 2 tbsp unsalted butter
06 - 1 tsp sugar
→ Sandwich Assembly
07 - 8 slices rye bread or sourdough
08 - 8 slices Swiss cheese or American cheese
09 - 4 tbsp unsalted butter, softened
→ Optional
10 - 1 tbsp Dijon mustard
11 - 1 tbsp mayonnaise
# How-To Steps:
01 - Melt 2 tablespoons butter in a large skillet over medium-low heat. Add thinly sliced onions and sugar. Cook, stirring frequently, until onions turn deeply golden and caramelized, approximately 20 to 25 minutes. Set aside.
02 - Season ground beef with salt and black pepper. Form into four thin, oval-shaped patties matching the size of bread slices.
03 - Heat a separate skillet or grill pan over medium-high heat. Cook patties for 2 to 3 minutes per side until browned and cooked through. Remove from heat.
04 - Arrange eight bread slices. Spread softened butter thinly on one side of each slice. Optionally, spread Dijon mustard or mayonnaise on the unbuttered side. Layer four slices with one cheese slice, one beef patty, a generous portion of caramelized onions, and another cheese slice. Top with remaining bread slices, buttered side outward.
05 - Preheat a clean skillet or griddle over medium heat. Grill sandwiches 2 to 3 minutes per side, pressing gently until bread turns golden brown and cheese melts.
06 - Remove sandwiches from heat and allow to rest for 1 to 2 minutes. Slice in half and serve immediately.