In a large pot, over medium heat, cook the 6 slices of bacon until crispy, about 8-10 minutes. Remove and crumble.
Pour out most of the bacon fat, leaving 1 tablespoon. Melt 4 tablespoons of unsalted butter in the pot, add diced onion, cook until soft, about 3-4 minutes. Stir in minced garlic and sauté for 30 seconds.
Sprinkle ¼ cup of all-purpose flour over the mixture, stirring constantly for 1-2 minutes.
Gradually whisk in 3 cups of chicken broth, bringing to a gentle boil.
Add 4 cups of peeled and diced russet potatoes. Reduce heat, cover, and simmer for 15-20 minutes until tender.
Lightly mash the potatoes in the pot for desired consistency.
Stir in 1 cup of heavy cream, 1 cup of shredded cheddar cheese, and ½ cup of sour cream. Add salt and pepper to taste, and heat until cheese melts.
Ladle soup into bowls and top with crumbled bacon, sliced green onions, and additional cheese.
Notes
For best results, ensure bacon is crispy and whisk the broth gradually to avoid lumps.