Scrub potatoes and wrap in foil. Bake 1 hour at 400 degrees or until soft. Cut in half, lengthwise, and scoop out potato. Mash and add warm milk until smooth consistency. Add butter and onion salt to taste. Put back into potato skins. Cover with foil. Reheat, covered 325- 350 degrees for 30 minutes. May make ahead and keep in refrigerator until ready to heat. Top with fried bacon bits, cheddar cheese or dot of butter.