In a skillet, brown the ground beef with onions; drain. Place potatoes and seasoning mix in the slow cooker; cream of celery soup. Top potato mixture with ground beef and onions; salt and pepper to taste. Dot evenly with ketchup and mustard; top with cheese slices. Cover and cook on low for 4 to 6 hours.
Note: Feel free to add a vegetable to this recipe. Simply add it withthe soup. This recipe could use any boxed potatoes wit success. Feel free to season hamburger as you would if you were making cheeseburgers.