Place potatoes in a large pot. Cover with water. Add salt. Bring to a boil. Cover, turn down to a simmer. Cook for 10 minutes or until potatoes are soft. Drain. Return to pan. Mash potatoes. Add milk, cheese and butter. Stir well. Preheat broiler to high. Slice hot dogs lengthwise - but not all the way through. Spoon potatoes into the hot dogs. Place on baking sheet. Broil for 3 minutes.