Pierce potatoes multiple times with a fork.
Microwave the potatoes for 12 to 15 minutes or until tender (or bake in the oven at 350°F for 45 minutes).
Carefully half the potatoes and cool.
Once cool enough to handle remove the skins and cut into chunks.
Cook the bacon in a skillet over medium heat until crisp.
Transfer to a paper towel lined plate.
Reserve 1 Tablespoon of the bacon fat and discard the rest.
Once bacon has cooled crumble into small pieces.
In a Large pot, melt butter over med-low heat.
Add the bacon fat and onion, cook for 2 to 3 minutes or until onion is tender.
Add Garlic and cook until fragrant, about 30 seconds.
Slowly whisk the flour into the pan and stir continuously for 1 to 2 minutes.
Slowly whisk in the milk and Half & Half.
Keep whisking until smooth.
Gradually add in the chicken stock and bring to a light simmer.
Whisk in the kosher salt, garlic salt and pepper.
Keep at a light simmer until mixture has thickened slightly about 5-7 minutes.
Reserve 1/4 C each of the cheeses and 1/4 C bacon for garnish.
Mix the remaining cheese and bacon and sour cream into the pot.
Remove from heat.
Scoop potato chunks into pot breaking into small pieces and mix.
Serve hot and top with the reserved cheese and bacon.