In a large bowl, combine the ground beef, egg, breadcrumbs, onion, tomato paste, Worcestershire sauce, Italian seasoning, salt, and pepper. Form the mixture into 4 equal sized, oval shaped patties.

Heat the cooking oil in a large pan over medium heat. Cook the patties for 5 to 6 minutes on each side. Remove the steaks to a waiting plate. Set aside.

In a measuring cup or small bowl, whisk together the beef broth, flour, and Worcestershire sauce and Dijon Mustard. Set aside.

Using the same pan you used to cook the patties, melt the butter over low-medium heat, then add the onion, mushrooms, salt, and pepper. Cook for 4 to 5 minutes until the onions and mushrooms begin to soften. Slowly pour in the beef broth mixture. Stir to combine.

Add the patties back to the pan, and simmer over medium heat for an additional 10 to 12 minutes until the gravy begins to thicken. Stir the gravy as needed to ensure it doesn’t stick and burn. Let the gravy reduce by about half then remove it from heat. It will thicken more as it cools.

Serve the patties with the gravy over mashed potatoes.