Instructions

1. Preheat your grill or skillet over medium-high heat.
2. In a bowl, season the ground beef with salt and pepper. Mix gently and form into 4 equal-sized patties, making a slight indentation in the center of each patty to prevent them from puffing up while cooking.
3. Heat the olive oil in a skillet over medium heat. Add the patties and cook for about 4-5 minutes on each side, or until they reach your desired level of doneness. For medium, aim for an internal temperature of 160°F (71°C).
4. Once cooked, remove the patties from the skillet and cover them loosely with foil to keep warm.
5. In the same skillet, add the sliced onions and cook, stirring occasionally, until they are caramelized and golden brown, about 10 minutes. You can add a pinch of salt to help the onions release their moisture.
6. While the onions are caramelizing, place a slice of provolone cheese on each patty and cover the skillet with a lid for about 1 minute to allow the cheese to melt.
7. To prepare the au jus, combine the beef broth and Worcestershire sauce in a small saucepan. Bring to a simmer over medium heat and let it warm through.
8. To assemble the burgers, place each patty on a hamburger bun, top with a generous portion of caramelized onions, and serve with a small bowl of au jus on the side for dipping.