Place bacon pieces in a large Dutch Oven or soup pot over medium heat and cook until bacon is crisp and browned. Remove bacon pieces and set aside, leaving the fat in the pot.
Add butter and chopped onion and cook over medium heat until onions are tender (3-5 minutes).
Sprinkle the flour over the ingredients in the pot and stir until smooth (use whisk if needed).
Add diced potatoes to the pot along with chicken broth, half and half, salt, pepper, and ancho chili powder. Stir well.
Bring to a boil and cook until potatoes are tender when pierced with a fork (about 10 minutes). Reduce heat to simmer and remove approximately half*** of the soup to a blender and puree until smooth (half is about 5 cups of soup. (Alternatively you can use an immersion blender).
