In a large bowl, combine beef, grated onion, salt and pepper. Divide meat into 6 portions and shape into patties about 3/4 inch thick. Cook steaks in caste iron fry pan or heavy skillet until cooked through, but don’t dry out. Set aside.
In same skillet, add just a bit of butter and sauté mushrooms, scraping edges to get all the beef drippings included. Add red wine if desired and scrape one more time.
Prepare gravy as per package instructions. Add to mushroom mixture and sour cream and mix well. Return the steaks to the skillet and simmer for a few minutes to heat through.