Bake, peel, and mash up potatoes. Melt butter, mix in flour, stirring until smooth, then cook 1 minute, stirring constantly. Gradually add 6 cups milk; cook over medium heat, stirring often, until thickened and bubbly. Add potatoes, salt, pepper, 2 tablespoons of green onion, 1/2 cup bacon and 1 cup of cheese. Cook until thoroughly heated. Stir in sour cream. Add extra milk for desired consistency, if necessary. Add more salt and pepper to desired taste. Serve topped with bacon, cheese, and green onions. I usually cook more bacon than this calls for so that I have more to use as a topping.