Begin by placing the bacon pieces in a large Dutch oven or a soup pot over medium heat. Cook the bacon until it becomes crisp and browned, releasing its flavorful fat. Once done, remove the bacon pieces and set them aside, keeping the rendered fat in the pot.

Next, add the butter to the pot, allowing it to melt and mingle with the bacon fat. Stir in the chopped onion and cook over medium heat until the onions become tender, which should take about 3 to 5 minutes. Follow by adding the minced garlic and cooking until it becomes fragrant, approximately 30 seconds.

Sprinkle the flour over the sautéed ingredients, stirring until you achieve a smooth consistency. If needed, use a whisk to ensure there are no lumps. Add the diced potatoes, chicken broth, milk, heavy cream, salt, pepper, and ancho chili powder to the pot. Stir everything together thoroughly.

Bring the mixture to a boil and cook until the potatoes are fork-tender, which should take around 10 minutes. Once the potatoes are soft, reduce the heat to a simmer. Carefully remove about half of the soup and transfer it to a blender, being cautious of the hot liquid. Puree the soup until smooth. If you prefer, you can use an immersion blender instead.

Return the pureed soup to the pot, then stir in the sour cream and the reserved bacon pieces. Allow the soup to simmer for an additional 15 minutes, letting the flavors meld together.

Serve the soup topped with your choice of shredded cheddar cheese, chives, more sour cream, or additional bacon. Enjoy the rich, comforting flavors!