# 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 Prepare:
01 - Melt 2 tbsp butter over medium-low heat in a large skillet. Add sliced onions and sugar, stirring often, and cook until deeply golden and caramelized, about 20–25 minutes. Remove from heat and set aside.
02 - Season ground beef with salt and black pepper. Form into four thin oval patties approximately the size of bread slices.
03 - Heat a skillet or grill pan over medium-high heat. Cook patties for 2–3 minutes per side until browned and just cooked through. Remove from heat.
04 - Arrange eight bread slices. Spread a thin layer of butter on one side of each. Optionally, spread Dijon mustard or mayonnaise on the opposite, unbuttered side.
05 - On four bread slices (unbuttered side up), layer one slice of cheese, a cooked patty, a generous spoonful of caramelized onions, and another cheese slice. Top each with remaining bread slices, buttered side facing out.
06 - Heat a clean skillet or griddle over medium heat. Cook sandwiches for 2–3 minutes per side, pressing gently, until bread is golden and cheese has melted.
07 - Remove sandwiches from heat, let rest for 1–2 minutes, then slice in half and serve warm.