Place bacon pieces in a large Dutch oven or soup pot over medium heat and cook until crisp and browned, then remove with a slotted spoon and set aside, leaving the rendered fat in the pot.

Add butter and chopped onion to the pot with the reserved bacon fat. Cook over medium heat for 3–5 minutes until onions are tender, then stir in minced garlic and cook another 30 seconds until fragrant.

Sprinkle the all‑purpose flour over the mixture and stir constantly until smooth to form a roux.

Add the diced potatoes, chicken broth, milk, heavy cream, salt, pepper, and optional ancho chili powder. Stir to combine thoroughly.

Bring the soup to a boil, then reduce heat to a simmer and cook until the potatoes are fork‑tender, about 10 minutes.

Carefully remove approximately half of the hot soup and puree until smooth using an immersion blender or a standard blender, then return the pureed soup to the pot with the remaining chunky soup.

Stir in the sour cream and reserved crispy bacon. Allow the soup to simmer gently for another 15 minutes so the flavors meld together.

Serve hot in bowls and garnish with optional toppings like additional sour cream, shredded cheddar cheese, crisp bacon, or fresh chives.