Preheat your oven to 400°F (200°C).
Wash the potatoes thoroughly and pat them dry. Pierce each potato a few times with a fork.
Bake the potatoes directly on the oven rack for about 1 hour, or until they are tender when pierced with a fork.
Remove the potatoes from the oven and let them cool slightly. Reduce the oven temperature to 350°F (175°C).
Cut each potato in half lengthwise and scoop out the flesh into a mixing bowl, leaving a thin shell.
In the mixing bowl, add sour cream, milk, butter, salt, and pepper to the potato flesh. Mash until smooth.
Stir in half of the shredded cheese, half of the crumbled bacon, and half of the chopped chives.
Spoon the mixture back into the potato shells and place them on a baking sheet.
Top with the remaining cheese and bacon.
Bake for an additional 15-20 minutes, or until the cheese is melted and bubbly.
Garnish with the remaining chives before serving.