Bake the Potatoes (if not already done): Bake at 400°F (200°C) for 45–50 mins. Cool, peel, and roughly mash. Roasting creates a sweeter, more intense potato base.
Cook the Bacon: In a large pot, cook chopped bacon until crispy. Remove and set aside, reserving 1 tbsp of bacon fat in the pot.
Sauté Aromatics: Add butter to the bacon fat, then onions. Cook until soft, 3–4 minutes. Add garlic and stir for 30 seconds—don’t let it brown; garlic can turn bitter quickly.
Make the Roux: Sprinkle in flour, stirring constantly for 1–2 minutes until light golden—this thickens the soup without lumping.
Build the Soup Base: Slowly whisk in chicken broth. Bring to a simmer, then stir in milk and cream. Simmer gently for 5–7 minutes.
Add Potatoes & Blend Slightly: Stir in mashed baked potatoes. For a smoother texture, blend part of the soup using an immersion blender—leave some chunks for body.
Finish with Cheese & Seasoning: Stir in shredded cheddar, cooked bacon, salt, and pepper. Simmer for 2–3 more minutes until everything is creamy and rich.
Serve & Garnish: Ladle into bowls and top with sour cream, green onions, extra cheese, and bacon bits.