Ingredients:

  • 2 large (450g) yellow onions, thinly sliced
  • 2 tbsp (28g) unsalted butter
  • 1/2 tsp (3g) salt
  • 1 tsp (5ml) balsamic vinegar
  • 1.5 lbs (680g) ground beef (80/20 blend)
  • 1 tsp (6g) kosher salt
  • 1/2 tsp (2g) cracked black pepper
  • 1/2 tsp (2g) garlic powder
  • 4 slices (110g) Swiss cheese
  • 4 brioche buns, split
  • 2 tbsp (28g) unsalted butter, softened
  • 1 cup (30g) fresh arugula
  • 1 tbsp oil (for searing)

Instructions:

  1. Melt 2 tbsp (28g) of butter in a cast iron skillet over medium-low heat.
  2. Add sliced onions and salt, stirring occasionally for 20–30 minutes until they reach a deep mahogany-colored jam consistency.
  3. Stir in the balsamic vinegar to deglaze the pan, then remove onions from the pan and set aside.
  4. Gently mix ground beef with salt, pepper, and garlic powder. Divide into 4 equal portions and shape into 3/4 inch thick patties, pressing a small indentation into the center of each.
  5. Heat the skillet to medium-high with a splash of oil and sear patties for 3–5 minutes per side until a dark brown crust forms.
  6. During the last 2 minutes of cooking, place a slice of Swiss cheese on each patty and cover with a lid for 30 seconds to melt.
  7. Remove patties, wipe the skillet, and toast the brioche buns in the remaining butter until golden brown.
  8. Assemble by placing the patty on the bun bottom, topped with caramelized onions and fresh arugula.