In your cast iron skillet or nonstick skillet, add butter, Worcestershire sauce, red wine vinegar, and sliced onions over low heat. Stir onions until fully coated in melted butter. Continue to cook onions over low heat until caramelized, stirring occasionally. Add minced garlic once the onions become tender.
In a small bowl, mix garlic powder, salt and pepper. Rub pork chops all over with mustard. Season all sides of pork chops with seasonings.
When onions are done caramelizing, stir in 2 tbsp beef broth and dried thyme. Remove onions from skillet and transfer to a bowl.
Heat 1 tbsp oil over medium heat in the same skillet you cooked the onions. Carefully add pork chops to hot skillet and cover with lid. Cook for 3-4 minutes until golden on bottom. Flip pork chops over, cover and cook another 3-4 minutes and pork chops are cooked through to 155 degrees.
Add onions back to the skillet with the pork chops along with remaining beef broth. Once French onion sauce begins to lightly simmer, remove from heat.
Serve pork chops with French onion sauce over mashed potatoes or with your favorite side dishes.