In a large skillet over medium high heat, heat oil. Add onion, bell peppers, and mushrooms, season with salt and pepper, and cook for 4-5 minutes, stirring often, until just softened and browned a bit on the edges. Remove to a plate and cover with foil to keep warm.

Return the skillet to the heat and add the beef, cooking 6-8 minutes until no longer pink. Season with salt and pepper, then stir in the garlic and cook for 30 seconds, until fragrant. Drain excess fat.

Stir in beef broth, tomato paste, and Worcestershire and season generously with salt and pepper. Simmer until most of the liquid has reduced, 2 minutes.

Add Velveeta, mixing until it’s melted. Remove the skillet from the heat, lay provolone slices on top, and cover until melted. Serve hot beef on toasted hamburger buns, topped with onions and peppers.