Follow these straightforward steps to create your delicious French Onion Burgers:

1. Caramelize Onions: In a skillet over medium heat, melt the butter. Add the thinly sliced onions, sprinkle with salt, and cook until soft and caramelized, about 15-20 minutes. Stir occasionally to prevent burning.
2. Prepare the Burger Patties: In a bowl, mix the ground beef with black pepper, garlic powder, and Worcestershire sauce. Form the mixture into four equal patties.
3. Cook the Patties: In a separate skillet or grill, cook the burger patties over medium-high heat to your desired doneness, approximately 4-5 minutes per side for medium-rare.
4. Add Cheese: When the patties are almost done cooking, place a slice of Swiss cheese on each patty. Cover the grill or pan to melt the cheese, about 2 minutes.
5. Toast the Buns: While the cheese melts, lightly toast the hamburger buns on a pan or grill until golden brown.
6. Assemble the Burgers: Place each patty on a bun, and top generously with caramelized onions. Drizzle with balsamic glaze if desired.
7. Garnish and Serve: Add chopped parsley for a fresh touch. Serve with your favorite sides and enjoy!