Ingredients:

  • 1 lb (450g) Ground Beef (80/20 ratio recommended)
  • 1/2 cup (60g) Plain breadcrumbs (Panko or standard)
  • 1/4 cup (60ml) Whole Milk
  • 1 large Egg, lightly beaten
  • 1/4 cup (40g) Finely diced yellow onion
  • 1 tbsp (15ml) Worcestershire Sauce
  • 1 tsp (5ml) Ketchup or Tomato Paste
  • 1 tsp (5g) Kosher Salt
  • 1/2 tsp (2.5g) Freshly Ground Black Pepper
  • 1/4 tsp Garlic Powder
  • 1 tbsp (15ml) Olive Oil or neutral oil (for frying)
  • 2 large Yellow Onions, thinly sliced
  • 2 tbsp (30g) Unsalted Butter (for onions)
  • 1 tsp (5ml) Balsamic Vinegar (optional)
  • Pinch of Salt and Black Pepper (for onions)
  • 8 slices Marble Rye or Pumpernickel Bread
  • 4 tbsp (60g) Unsalted Butter, softened (or Mayonnaise, for grilling exterior)
  • 8 slices Swiss Cheese (or Provolone)

Instructions:

  1. Start the Onions: Melt the 2 tbsp of butter in a heavy-bottomed skillet over medium-low heat. Add the sliced onions, salt, and pepper. Cook low and slow, stirring occasionally, for 30–40 minutes until deeply mahogany brown and tender. Stir in the balsamic vinegar (if using) just before removing from heat. Set aside.
  2. Soak the Binder: In a mixing bowl, combine the breadcrumbs and milk. Let sit for 5 minutes until the breadcrumbs are fully saturated and paste-like.
  3. Create the Mix: Add the ground beef, beaten egg, diced onion, Worcestershire, ketchup, salt, pepper, and garlic powder to the breadcrumb mixture.
  4. Mix Gently: Using your hands, mix the ingredients just until combined. Crucially, do not overmix, as this will result in tough patties.
  5. Form and Chill: Divide the mixture into 4 equal portions. Form them into oval or rectangular patties, about 3/4 inch thick. Place on a parchment-lined tray and chill in the refrigerator for a minimum of 30 minutes to help them hold their shape.
  6. Heat the Pan: Heat the 1 tbsp of olive oil in the same skillet (wipe clean if necessary) over medium-high heat.
  7. Sear: Place the chilled patties into the hot oil, ensuring not to overcrowd the pan. Sear for 4–5 minutes until a deep brown crust forms.
  8. Flip and Finish: Flip the patties and reduce the heat slightly to medium. Cook for another 5–7 minutes, or until the internal temperature reaches 160°F (71°C). Remove the cooked patties and set them aside.
  9. Prepare the Bread: Spread the softened butter or mayonnaise evenly on one side of each slice of bread (this will be the grilling side).
  10. Build the Sandwich Base: Flip 4 slices of bread butter-side down in the clean skillet or onto a griddle set to medium heat. Immediately top each slice with one piece of Swiss cheese.
  11. Layer Up: Place one meatloaf patty on top of the cheese, then generously mound the warm caramelised onions on the patty. Top the onions with the second slice of Swiss cheese.
  12. Close and Grill: Place the remaining slices of bread (butter-side up) on top of the stacks. Grill for 3–4 minutes per side, gently pressing down, until the bread is golden brown and crisp, and the cheese is fully melted and gooey.
  13. Serve: Remove from the pan, slice diagonally, and serve immediately.