Preheat your oven to 400°F (200°C).
Wash and dry the potatoes. Pierce each potato several times with a fork.
Place the potatoes on a baking sheet and bake for about 1 hour, or until tender.
Remove the potatoes from the oven and let them cool slightly. Cut each potato in half lengthwise and scoop out the flesh into a mixing bowl, leaving a thin shell.
In the mixing bowl, combine the potato flesh, sour cream, milk, butter, salt, and pepper. Mash until smooth.
Stir in half of the shredded cheese and half of the crumbled bacon.
Spoon the mixture back into the potato shells. Top with the remaining cheese and bacon.
Return the potatoes to the oven and bake for an additional 15 minutes, or until the cheese is melted and bubbly.
Garnish with chopped chives before serving.