In a large shallow bowl, combine flour with black pepper, salt, onion powder, and garlic powder.
Pat dry the steak with paper towels and dredge steaks in the flour mixture.
Place a large skillet over medium-high heat and add the butter. Once melted, brown the steak on each side.
Transfer steaks to a 6-qt. slow cooker. Add the sliced onion, mushrooms, and celery.
Mix the condensed soup with the beef broth until combined and pour over the steaks.
Cover and cook on low for 8-9 hours or on high for 5-6 hours, or until the meat is fork-tender.
Serve with mash potatoes and top with the formed gravy. Garnish with parsley.
