Brown the beef on a large cast iron pan and transfer to a plate. Melt the butter on the same pan then add the onions, bell peppers and mushrooms. Let brown for few minutes then add the beef back to the pan.
Mix the beef broth and cornstarch. Stir in the broth, ketchup, Worcestershire sauce and season with salt and pepper. Cook until lightly thickened. Turn off heat and stir in the provolone cheese. Serve on toasted buns. Yum!
Recipe by Gluten-Free by Jan at https://glutenfreebyjan.com/gluten-free-philly-cheese-steak-sloppy-joes/