Heat 2 tablespoons of olive oil in a large skillet over medium heat until it shimmers. Add 2 thinly sliced onions and cook for 10–12 minutes, stirring frequently, until they are golden brown and caramelized.

Stir in 2 minced garlic cloves and continue to sauté for an additional 1–2 minutes until fragrant and slightly golden.

Add 1 pound of ground beef and break apart with a spatula while cooking for 5–7 minutes, or until fully browned.

Carefully drain excess grease if necessary to maintain flavor without greasiness.

Stir in 2 tablespoons of Worcestershire sauce, a splash of soy sauce, 1 teaspoon of fresh thyme, and season with salt and pepper. Simmer for about 5 minutes.

While mixture simmers, toast hamburger buns until lightly golden, about 2–3 minutes.

Spoon beef mixture onto the bottom half of each toasted bun and top with slices of Swiss cheese.

Optionally, sprinkle with chopped parsley before serving.