# What You'll Need:
→ Beef
01 - 1.1 lbs ground beef (80/20 blend)
02 - 1/2 teaspoon salt
03 - 1/2 teaspoon black pepper
→ Onions
04 - 2 large yellow onions, thinly sliced
05 - 2 tablespoons unsalted butter
06 - 1 teaspoon sugar
→ Sandwich Assembly
07 - 8 slices rye or sourdough bread
08 - 8 slices Swiss or American cheese
09 - 4 tablespoons unsalted butter, softened
→ Optional
10 - 1 tablespoon Dijon mustard
11 - 1 tablespoon mayonnaise
# How To Make:
01 - Melt 2 tablespoons butter in a large skillet over medium-low heat. Add sliced onions and sugar; stir frequently and cook until deep golden brown and caramelized, about 20 to 25 minutes. Remove from heat and set aside.
02 - Season ground beef with salt and pepper. Form into 4 thin oval patties matching the size of the 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 - Butter one side of each bread slice thinly. Optionally spread Dijon mustard or mayonnaise on the unbuttered side. On 4 unbuttered bread slices, layer a slice of cheese, a patty, caramelized onions, and another slice of cheese. Top with remaining bread slices, buttered side out.
05 - Heat a clean skillet or griddle over medium heat. Grill sandwiches for 2 to 3 minutes per side, pressing gently, until bread is golden and cheese melts.
06 - Remove sandwiches from heat and allow to rest for 1 to 2 minutes. Slice in half and serve warm.