In a large Dutch oven or soup pot, cook the 6 slices of chopped bacon over medium heat for 6 to 8 minutes until crisp. Remove bacon with a slotted spoon to a paper towel-lined plate, leaving 2 tablespoons of bacon grease in the pot.

Add 1 diced yellow onion and 2 diced celery stalks to the reserved bacon grease. Cook over medium heat for 5 minutes until the vegetables are softened.

Stir in 3 cloves of minced garlic and cook for 1 minute until fragrant. Sprinkle 0.25 cup of all-purpose flour over the vegetables and stir constantly for 1 minute to cook out the raw flour taste.

Slowly pour in 4 cups of chicken broth and 2 cups of whole milk, whisking continuously to smooth out any lumps. Add 3 pounds of peeled, cubed Russet potatoes, 1 teaspoon of salt, and 0.5 teaspoon of black pepper.

Bring the soup to a boil over medium-high heat. Reduce heat to medium-low, cover partially with a lid, and simmer for 15 to 20 minutes until the potatoes are fork-tender.

Use a potato masher to mash about half of the potatoes directly in the pot to reach your desired thickness while keeping some tender chunks.

Remove pot from heat and stir in 1 cup of shredded sharp cheddar cheese and 0.5 cup of sour cream until completely melted and smooth.

Ladle hot soup into bowls and garnish with reserved cooked bacon and 3 tablespoons of finely chopped fresh chives.