Season pork chops uniformly on both sides with salt and black pepper.
Heat olive oil in a large oven-safe cast iron skillet over medium-high heat and sear pork chops for 4 minutes per side until a Maillard crust forms; remove and set aside.
Reduce heat to medium and add butter and onions to the skillet; cook for 20 minutes, stirring frequently, until onions are deep mahogany and caramelized.
Add minced garlic and dried thyme to the onions, sautéing for 60 seconds until aromatic.
Deglaze the skillet with beef broth and Worcestershire sauce, scraping the bottom of the pan to incorporate the fond.
Return the pork chops to the skillet, nestling them into the onion mixture.
Distribute shredded Gruyere cheese evenly over each pork chop.
Transfer the skillet to a preheated broiler for 2 to 3 minutes until the cheese is melted, bubbling, and lightly browned.
Let the dish rest for 5 minutes before service to allow the juices to redistribute.