Pierce the potatoes with a fork several times, then microwave them for 12 to 15 minutes until tender. Let them cool slightly, cut them in half, and scoop out the flesh into chunks once they are cool enough to handle.

While the potatoes cook, heat a skillet over medium-high heat and fry the bacon until crisp. Once done, transfer the bacon to a plate lined with paper towels to drain. Reserve 1 tablespoon of the bacon grease from the pan, and discard the rest. Once cooled, crumble the bacon into pieces.

In a large pot, melt the butter over medium-low heat. Add the reserved bacon fat along with the minced garlic and diced onion. Cook for about 2 to 3 minutes until the onion softens. Slowly whisk in the flour, stirring for 1 to 2 minutes until fully incorporated.

Gradually whisk in the milk and half-and-half, continuing to whisk until smooth. Slowly pour in the chicken stock, stirring to combine. Simmer the mixture for 5 to 7 minutes until it thickens slightly, then season with the salt, garlic salt, and black pepper.

If you'd like to garnish the soup, set aside 1/4 cup of each cheese and some bacon pieces. Stir the rest of the cheese, bacon, and sour cream into the soup, then remove the pot from heat.

Add the cooked potato chunks to the pot, breaking them into smaller pieces or leaving them chunky, based on your preference. Serve the soup hot, topped with the reserved cheese, bacon, and fresh chives.