Careful, not too much water! In large soup kettle, sauté onion in melted butter. Peel potatoes and cut in small pieces. Add to onions and cover with hot water. Season with garlic salt and pepper. Cook until mushy. Stir in cream of chicken soup and add pieces of cheese. Stir till cheese is melted. Stir in milk. Heat to boiling. Remove from heat. Serve with crackers. May be made a day in advance to heat up.