01 - In a large Dutch oven or heavy-bottomed pot over medium heat, cook chopped bacon until deeply browned and crisp, approximately 6 to 8 minutes. Remove bacon with a slotted spoon and transfer to a paper towel-lined plate, reserving 2 tablespoons of rendered fat in the pot.
02 - Add diced onion to the reserved bacon fat and cook, stirring frequently, until softened and translucent, about 4 minutes. Stir in minced garlic and sauté for 30 seconds until aromatic.
03 - Add peeled and cubed potatoes to the pot along with chicken broth. Bring mixture to a boil, reduce heat to medium-low, and simmer uncovered for 15 to 20 minutes or until potatoes are exceptionally tender and begin to break apart.
04 - In a small bowl, whisk flour or cornstarch with 1/2 cup of milk until smooth and lump-free. Stir this slurry into the simmering soup, followed by the remaining milk and heavy cream. Continue cooking for 5 minutes, stirring occasionally, until the soup thickens.
05 - Remove pot from heat. Gradually stir in the shredded cheddar cheese until melted and the soup is smooth. Season with salt and freshly ground black pepper to preferred taste. For a chunkier texture, lightly mash some of the potatoes with a fork in the pot.
06 - Ladle hot soup into serving bowls. Top generously with sour cream, reserved crispy bacon, fresh chives, and sliced green onions. Offer extra shredded cheese and crusty bread or dinner rolls alongside.