Preheat oven to 450 degrees F (230 degrees C). Lightly grease a 2 quart baking dish, and set aside. Line a baking sheet with aluminum foil. Pierce each sweet potato several times with a fork, and place on the prepared baking sheet.
Roast the sweet potatoes in preheated oven until easily pierced with a fork, 1 to 1 1/2 hours. Remove from the oven, and cool about 15 minutes. Reduce oven temperature to 350 degrees F (175 degrees C).
When sweet potatoes are cool enough to handle, cut in half, and scoop flesh into a mixing bowl. Discard potato skins. Beat the sweet potatoes with the chipotle peppers, butter, and salt; spread evenly in the prepared baking dish. This can baked now or refrigerated until the next day.
Bake in the preheated oven until heated through, 20 to 25 minutes.
