1. In a large skillet over medium-low heat, melt the butter. Add the sliced onions and a pinch of salt. Cook for 25–30 minutes, stirring often, until deeply golden and caramelized.

2. Push the onions to one side of the skillet. Add ground beef and cook until browned, breaking it apart with a spatula.

3. Stir in minced garlic and dried thyme. Cook for 1 minute until fragrant.

4. Sprinkle flour over the meat and stir well to coat. Cook for another minute.

5. Pour in beef broth and Worcestershire sauce. Scrape up any brown bits from the skillet and stir. Simmer for 5–7 minutes until thickened.

6. Preheat broiler. Spoon the beef mixture onto the bottom halves of the slider buns on a baking sheet.

7. Sprinkle shredded cheese over the top and broil for 1–2 minutes until melted.

8. Add bun tops and serve hot, garnished with parsley if desired.