If beginning with uncooked potatoes, boil or microwave until just fork tender. Cut into bite-sized pieces; reserve.
Brown bacon then remove to paper towels to drain. Pour off bacon drippings, leaving 1 Tbl. in soup pan; reserving the rest.
Add onion, carrots and celery and sauté until carrots are softened; 8-10 minutes. Add garlic and sauté an additional minute, stirring frequently. Add 2 Tbl. reserved bacon drippings and cooked potatoes. Sauté for 2-3 minutes. Dust mixture with flour and cook two minutes, stirring frequently.
Whisk in broth and milk; bring to a gentle boil. Add in sour cream; reduce to a simmer and assess thickness. If thicker soup is desired, use an immersion blender to puree some of the veggies.
Season with salt & pepper to taste. Serve with sprinkle of crumbled bacon, snipped chives and shredded cheese, if desired.