In a large pot or Dutch oven over medium heat, cook the chopped bacon until crisp. Transfer the bacon to a paper towel-lined plate, leaving 1 to 2 tablespoons of bacon drippings in the pot.

Add the butter and diced onion to the pot. Cook for 4 to 5 minutes, stirring occasionally, until the onion is softened. Stir in the garlic and cook for 30 seconds.

Sprinkle the flour over the onions and stir constantly for 1 minute to form a light roux.

Gradually whisk in the chicken broth, scraping up any browned bits from the bottom of the pot. Add the potatoes, salt, black pepper, smoked paprika, and thyme.

Bring the soup to a boil, then reduce the heat to medium-low. Simmer for 15 to 20 minutes, or until the potatoes are very tender.

Use a potato masher to lightly mash some of the potatoes in the pot for a thicker texture, leaving plenty of chunks for a hearty soup.

Stir in the milk and heavy cream. Heat gently over low heat until warmed through, but do not boil.

Add the shredded cheddar cheese and stir until melted. Remove the pot from the heat, then stir in the sour cream until smooth. Taste and adjust seasoning if needed.

Ladle the soup into bowls and top with the cooked bacon, green onions, and additional cheddar cheese before serving.