In 4-cup measuring cup, mix broth and half-and-half. Gradually add broth mixture to onion mixture, cooking and stirring with whisk about 3 minutes or until mixture begins to thicken. Stir in dressing mix and cheese; cook until cheese is melted. Add frozen potatoes; cook and stir 2 to 3 minutes or until potatoes begin to thaw. Stir in sour cream and reserved bacon. Pour into ungreased 13x9-inch (3-quart) glass baking dish.