In a large skillet over medium heat, cook the thick-cut bacon until crispy, about 8-10 minutes. Remove and set aside, leaving drippings.
Peel and cube the russet potatoes. Boil with salted water until fork-tender, about 15-20 minutes. Drain and mash lightly.
In the skillet, melt butter over medium heat. Sauté the chopped onion until softened, about 5 minutes. Add garlic and cook for another minute.
Sprinkle flour into the skillet, stirring constantly for about 1 minute.
Gradually whisk in the chicken broth and half and half. Bring to a gentle boil, then lower heat and simmer for 10 minutes.
Stir in the mashed potatoes, sour cream, and pepper. Simmer for 5 minutes.
Blend the soup for a creamier consistency if desired.
Stir in shredded cheddar cheese until melted.
Ladle into bowls and top with bacon bits, extra cheese, and chives.