Place the bacon in a large roasting pan or Dutch oven and cook over medium-high heat, turning occasionally, until evenly browned, about 10 minutes.
If you have an excessive amount of grease, drain the grease leaving a few tablespoons remaining.
Transfer bacon to a paper towel-lined plate to drain.
Cook and stir the white onions and celery in the bacon drippings until tender, 5 to 10 minutes.
Add chicken broth and potatoes, and bring to a boil over heat.
Reduce heat and simmer until potatoes are fork tender.
This will take about 20-30 minutes depending on heat.
Mash about one-third of the potatoes with a potato masher.
Add pieces of roasted garlic sliced lengthwise.
Reduce heat to low. In a large bowl, combine flour, salt and pepper, and dry ranch mix.
Whisk in the half-and-half and sour cream, beating well to combine thoroughly.
Slowly whisk sour cream mixture into the soup.
Add cheese.
Gently heat soup over low heat to warm, DO NOT BOIL!
Season soup with salt and pepper.
Top with green onions, cheese and bacon before serving.