Pierce potatoes with a fork and microwave for 12-15 minutes until tender. Let cool, remove skins, and cut into chunks.
Cook bacon in a skillet until crisp. Reserve 1 tbsp bacon fat and crumble the bacon once cooled.
In a large pot, melt butter over medium-low heat.
Add reserved bacon fat, garlic, and onion. Cook until onion is tender.
Whisk in flour, then gradually add milk, half-and-half, and chicken stock. Simmer until slightly thickened, about 5-7 minutes.
Stir in cheeses, bacon, and sour cream. Add potato chunks and stir to your desired consistency.
Serve hot, garnished with cheese, bacon, and chives.