Preheat oven to 350°F. Pierce skin of potatoes to prevent cracking while they bake.
Bake potatoes for 60 minutes or until fork tender. Remove from oven and allow to cool slightly.
Meanwhile, cook bacon. Allow to cool and finely chop.
Once potatoes are cooled enough to handle, slice in half lengthwise keeping skin in tact. Scoop white of potatoes into a mixing bowl, leaving ¼" on the skin.
Add sour cream, garlic powder, butter, and ½ of cheddar cheese, chives, and bacon to mixing bowl. Combine, adding milk until mashed potato consistency is reached (you may not need all milk).
Scoop (or pipe) mixture back into potato skins. Top with remaining cheese and bacon, then return to oven for 10-15 minutes or until cheese is melted and tops are golden brown.
Garnish with remaining chives before serving.
Notes
If freezing, allow to completely cool after adding mixture to back to the potato skins. Freeze on a baking sheet before adding to a freezer bag. To bake from frozen, preheat oven to 350°F. Bake twice baked potatoes for 25-30 minutes or until heated through and cheese is melted.