1 tablespoon olive oil
1 tablespoon butter
1 pound ground beef
1 tablespoon flour
1 onion, finely diced
1 tablespoon Worcestershire sauce
½ teaspoon salt
½ teaspoon black pepper
½ cup beef broth
8 ounces provolone cheese, grated
6 burger buns, toasted
Heat the olive oil in a skillet over high heat. Add the ground beef and brown very well on all sides. Remove the beef, leaving the fat behind.
Reduce the heat to medium, and add the butter to the skillet. Add the onions, and cook until caramelized, about 10 minutes. Sprinkle with the flour and mix well to combine.
Add the beef back to the pan and season with Worcestershire sauce, salt, and pepper. Add the beef broth and stir well, scraping to bring up the fond. Cook until the broth has reduced by half.
Remove from the heat, add the cheese, and stir until melted. Serve on toasted hamburger buns.