Place the potatoes on a baking sheet and bake for about 45 minutes. The exact baking time will depend on how large the potatoes are. The potato should be tender inside if you poke a fork into it.
Remove the potatoes from the oven and allow them to cool for 10 minutes.
Reduce the oven temperature to 350º F.
Slice potatoes in half lengthwise and use a spoon to scoop the flesh into a large bowl. Be sure to leave about ¼” of the flesh on the skins so the skins can hold the filling.
To the potato flesh add sour cream, cream cheese, milk, butter, bacon, chopped onions and 1 cup of cheese.
Use a potato masher to mash the mixture together until it is well mixed and as smooth as you’d like it. It’s ok to leave the potatoes a little chunky if you’d like...more make them completely smooth!
Spoon the mixture into the potato skins. Top each with remaining cheese and bacon.
Bake for an additional 10-15 minutes or until the cheese is melted.