In a large bowl, combine the ground beef, 1/4 can cream of mushroom soup, bread crumbs, egg, onions, and steak seasoning. Form into 4 oval patties and set aside.
In a large deep skillet over medium high heat, add 1 Tbsp canola oil and 1 Tbsp butter. Brown both sides of the patties and remove to a plate.
Add the remaining 1 Tbsp butter to the skillet and saute the mushrooms over medium heat until tender, about 8 minutes. Add the beef broth, gravy mix, remaining cream of mushroom soup, rosemary, and black pepper to taste, and whisk until smooth.
Add the browned patties back to the skillet and spoon the gravy over top. Cover with a lid and simmer for 20-25 minutes. Serve with mashed potatoes. Enjoy!