Place bacon in a large saute pan. Cook over medium heat until browned. Drain, crumble, and reserve.
In a stock pot, melt butter over medium heat. Add onion and saute until translucent. Whisk in flour until smooth. Gradually stir in milk, whisking constantly until thickened. Add chicken stock and simmer for 10 minutes.
Stir in cubed baked potatoes; bring back to a simmer, stirring frequently to avoid the milk burning on the bottom of the pan.
Simmer on low for 10 more minutes. Season with salt and pepper to taste.
Remove from heat. Add Cheddar and half the sour cream.
Garnish with crumbled bacon, reserved cheese, and reserved sour cream.
Notes
Baking Potatoes: Wash potatoes thoroughly with a stiff brush and cold running water. Dry, then using a standard fork poke 8 to 12 deep holes all over the spud so that moisture can escape during cooking. Place in a bowl and coat lightly with oil. Sprinkle with kosher salt. Heat convection oven to 375 degrees and position racks so that one rack can hold potatoes and one can hold a large sheet pan to catch drippings; you can bake the potatoes directly on the oven rack, or you can place them a few inches apart on an aluminum foil-lined baking sheet. Bake the potatoes for 50 to 60 minutes. Flip them over every 20 minutes or until interior of potato measures 210*F with a probe thermometer.