Heat olive oil in a large skillet over medium heat. Add sliced onions, stirring occasionally until they caramelize, about 10–12 minutes.

Stir in minced garlic with caramelized onions and cook for an additional 1-2 minutes.

Add ground beef to the skillet, breaking it apart and cooking until browned, about 5–7 minutes.

Lower heat and stir in Worcestershire sauce, soy sauce, dry thyme, salt, and pepper; let simmer for 5 minutes.

Preheat oven to 350°F (175°C). Toast hamburger buns on a baking sheet for about 5 minutes.

Scoop the beef and onion mixture onto the toasted buns, top with shredded Swiss cheese.

Sprinkle with fresh parsley for garnish and serve immediately.