In a skillet, cook the bacon until crispy.

Allow the bacon to cool and crumble it into small pieces. Place ½ of the crumbled bacon into a slow cooker and reserve the other ½ in the fridge for serving.

Add the onion, the celery, the garlic, and the potatoes into the slow cooker.

Add the broth, the parsley, the salt, and the pepper to the veggie mixture.

Place the lid on the slow cooker and cook on low-heat for 8 hours or high-heat for 4 hours.

Use a potato masher or an immersion blender to mash some of the potatoes in the slow cooker.

In a large skillet over medium-high heat, melt the butter until it begins to sizzle.

Whisk the flour into the butter for 1 minute.

Slowly, add the milk, ¼ cup at a time, whisking after each addition until the milk is completely mixed in.

Cook the mixture, while constantly whisking, until the sauce begins to thicken, about 5 minutes.

Turn off the heat and stir 2 cups of the cheese and the sour cream into the sauce mixture.

Mix the sauce into the soup and stir to combine.

Ladle the soup into bowls and top with the reserved bacon, the remaining cheese, and the chives.