Wash, dry, and bake potatoes for at least one hour at 350 degrees. You want the potatoes to be soft all the way through so they will be easy to scrape.
Meanwhile, combine all remaining ingredients except milk and onions in a large bowl.
Once potatoes are baked, cut in half lengthwise and scrape the piping hot innards into the bowl of goodness.
Use a potato masher and enough milk to make a creamy, smooth consistency.
Fill potato skins with the creamy potato mixture**, dot the top with the remaining 1 TBS butter, and bake for 20 minutes (or until really hot and slightly golden on top).
Top the potatoes with caramelized onions and serve!
**At this point, you may freeze the potatoes on a baking sheet, then wrap individually and stack in your freezer. Just remove from freezer and bake at 350 degrees until golden brown (about 45 minutes).