Pierce each potato 3 or 4 times with a fork, and place directly on oven rack. Bake potatoes at 450° for 1 hour and 5 minutes or until tender. Let cool slightly, about 20 minutes.
Cut baked potatoes in half lengthwise. Scoop pulp into a large bowl, reserving potato shells. Add butter and remaining ingredients to pulp, blending well with a potato masher or fork. Spoon potato mixture evenly into reserved shells; place on a baking sheet. Bake at 450° for 25 minutes or until golden.