Preheat oven to 400°F. Cut baked potatoes in half lengthwise. Scoop the filling into a large mixing bowl, leaving a shell to hold the filling when you bake the potatoes again.
Add the sour cream, milk, butter, half of the crumbled bacon, half of the shredded cheddar cheese, half of the chopped scallions, salt and pepper to the bowl with potatoes.
Mix using a potato masher until everything is combined and creamy. Spoon the potato mixture back into the potato shells, mounding it slightly in the middle.
Top each potato with the remaining shredded cheddar cheese and crumbled bacon and place them on a baking sheet. Bake for 15-20 minutes, until the cheese is melted and bubbly.