Ingredients:

  • 1.5 lb lean ground beef (85/15)
  • 1 tsp Worcestershire sauce
  • 1 tsp garlic powder
  • 1/2 tsp kosher salt
  • 1/2 tsp black pepper
  • 8 oz cremini mushrooms, sliced
  • 1 small yellow onion, thinly sliced
  • 1 tbsp unsalted butter
  • 1 tbsp olive oil
  • 4 slices Swiss cheese
  • Fresh parsley for garnish

Instructions:

  1. Toss the sliced mushrooms and onions in a bowl with olive oil and a pinch of salt and pepper. Note: This ensures every piece of veg is coated in fat for better flavor.
  2. Combine the ground beef, Worcestershire sauce, garlic powder, salt, and pepper in a mixing bowl.
  3. Gently mix the beef ingredients. Note: Do not overwork the meat or the burgers will be tough.
  4. Shape the beef into four 6 oz patties.
  5. Press a slight indentation into the center of each patty. Note: This prevents the burger from puffing up into a football shape.
  6. Cut four large squares of heavy duty aluminum foil.
  7. Place one patty in the center, top with the mushroom onion mix, and add one pat of butter.
  8. Fold and pinch the foil tightly to seal the pouch. Note: A tight seal is critical for trapping the steam.
  9. Bake at 400°F (200°C) on a baking sheet for 20-25 minutes until the foil feels tight and the beef is cooked through.
  10. Carefully open the packets, place one slice of Swiss cheese on each, and re seal for 2-3 minutes until the cheese is velvety and melted.