Peel and cut potatoes into medium chunks. Boil until soft. Drain well and add butter and onions. Add all parmesan cheese, half of cheddar cheese, salt and pepper and milk. Whip all together until smooth (will be thick).
Boil hot dogs, drain, slice half way through, and pull open. Spoon whipped potatoes into each hot dog until full. Sprinkle remaining cheese over all.
Bake at 325°F for 25 minutes. Serve with your favorite veggie and catsup to taste for kids; enjoy!