Heat a large skillet over medium heat. Continue to step 2 while the skillet is preheating.
Mix the ground beef, 2 tbsp of French onion soup, egg, bread crumbs, salt and pepper together.
Divide the meat into 8 sections and create an equal sized patty from each section.
add 1 tbsp of butter to the hot pan. Place the patties into the pan.
Brown on each side for approx 5-10 minutes or until the inside temperature reaches 165°. Remove the patties an set aside. Remove excess grease if needed.
Add the sliced onion and mushrooms. Sauté until tender.
Push the saute'd veggies to the back of the pan. In the front of the pan, melt the remaining 2 tbsp butter. Wisk in the 2 tbsp flour, allowing the roux to cook for 1-2 minutes.
Whisk in the beef broth, au jus seasoning mix, remaining french onion soup, Worcestershire sauce and dried parsley while incorporating the veggies.
Allow the gravy to boil until thickened to your liking.
Return the patties to the gravy. Dress with parsley, if desired. Serve over mashed potatoes or egg noodles.