In a large pot over medium heat, cook the bacon until crispy, about 8–10 minutes. Remove bacon and set aside, leaving about 1 tablespoon of bacon grease in the pot.

Add 4 tablespoons of butter to the pot with the reserved bacon grease. Once melted, add the chopped onion and minced garlic. Sauté for 5–7 minutes until translucent and fragrant.

Stir in 2 tablespoons of all-purpose flour into the sautéed onions and garlic, cooking for 1–2 minutes until it forms a light paste and turns golden.

Gradually whisk in 4 cups of chicken broth, breaking up any lumps. Bring to a gentle simmer for about 3–5 minutes.

Add 4 large russet potatoes, peeled and diced, to the pot. Bring to a boil, then reduce heat to simmer for about 15 minutes or until fork-tender.

Using an immersion blender, carefully blend the soup until smooth, approximately 1–2 minutes. For a chunkier texture, blend only partially.

Stir in 2 cups of milk, 1 cup of heavy cream, ½ cup of sour cream, and 1½ cups of shredded sharp cheddar cheese. Season with salt and pepper.

Crumble the reserved bacon and stir most of it into the soup. Simmer for an additional 2–3 minutes.

Ladle the soup into bowls and top with the remaining cheese, crumbled bacon, and chopped chives for garnish.