In a large skillet, heat the olive oil over medium heat. Add the chopped onion and sauté for about 5 minutes, or until the onion is soft and translucent.
Add the ground beef to the skillet, breaking it apart with a spatula. Cook until browned, about 6-8 minutes. Drain any excess fat.
Stir in the garlic powder, onion powder, Worcestershire sauce, beef broth, French onion dip, and Dijon mustard. Season with salt and pepper. Bring the mixture to a simmer and reduce the heat to low. Let it cook for about 10-15 minutes, stirring occasionally, until the mixture thickens slightly.
While the beef mixture is simmering, preheat your oven to 350°F.
Spoon the beef mixture onto the bottom half of each hamburger bun. Top with shredded Swiss cheese and place the tops of the buns on.
Arrange the assembled sandwiches on a baking sheet and bake in the preheated oven for about 10 minutes, or until the cheese is melted and bubbly.
Serve hot and enjoy!