Heat oven to 375 degrees Fahrenheit. Pierce the washed sweet potatoes with a fork so the steam can escape. Place the sweet potatoes in the oven on the oven rack and bake for about 45 minutes or until tender when pierced with a fork.
Remove the sweet potatoes from the oven and cut the potatoes lengthwise. Scoop out the potato flesh into a bowl, taking care to keep the skins intact. Mash the potatoes in a large bowl until there are no lumps.
dd in the sour cream and milk, then the brown sugar, butter and salt and mix until the potatoes are light and fluffy.
Put the potato skins in a baking dish. Refill the skins with the sweet potato mixture.
Turn the oven up to 400 degrees and bake the potatoes uncovered for about 25 minutes until they are golden brown.