Preheat oven 350 degrees. Grease a 3 qt casserole dish. Mix the milk with the cheddar cheese soup. Add the hot dogs, corn and onion. Pour into casserole dish.
Boil the water and butter on stove top. Remove from heat. add the potato flakes. Mix the milk and egg and add to potato mix. Stir in chives. Top the hot dog mixture with the potato mixture. Bake 30 minutes.
Add the shredded cheese and bake another 10 minutes until melted and bubbly