Cook Bacon: In a large Dutch oven or heavy soup pot, cook bacon slices over medium heat until crispy. Transfer to a paper towel-lined plate, crumble, and set aside. Pour off all but 1 tablespoon of bacon drippings from the pot.

Sauté Aromatics & Make Roux: Add butter to the pot and melt over medium heat. Add diced onion and cook for 3 to 4 minutes until translucent. Stir in minced garlic and cook 1 minute until fragrant. Sprinkle flour over the onions and stir constantly for 1 to 2 minutes to cook out raw flour flavor.

Add Liquid & Potatoes: Slowly pour in chicken broth and whole milk while whisking constantly to ensure a lump-free, velvety base. Add diced cubed Russet potatoes, salt, and black pepper.

Simmer Until Tender: Bring soup to a gentle boil, then reduce heat to medium-low. Simmer uncovered for 15 to 20 minutes, stirring occasionally, until potatoes are easily pierced with a fork.

Mash & Finish: Use a potato masher to mash about half of the potatoes directly in the pot, leaving delicious hearty chunks. Remove from heat and stir in sour cream, 1.5 cups of shredded cheddar cheese, and half of the crumbled bacon until cheese is melted and silky.

Ladle & Garnish: Ladle hot creamy soup into bowls. Top with remaining sharp cheddar cheese, crispy bacon crumbles, and fresh chopped chives. Serve warm!