Gradually add the milk, stirring constantly and cook over medium heat until the mixture thickens. Reduce the heat to medium low and stir in the potatoes, salt, pepper, ranch dressing mix (if using), 1 cup of the cheese, 1 cup of the bacon. Cook until the mixture is well heated, but not boiling.
Ladle into bowls and garnish with remaining cheese, bacon and green onions. Season with salt and pepper to taste, if needed.
My boys love to put ranch dressing on their baked potatoes so I decided to throw in some dry ranch dressing mix. This is totally optional and you don't have to, the flavor is not by any means overpowering, in fact if you didn't know it was in there, you probably wouldn't even be able to taste it.