In a large bowl, pour in 4 cups of Rice or Corn Chex Cereal. Set aside.
Over a double broiler, or in the microwave in 20 second intervals, melt the butter, chocolate chips, and Nutella. Make sure to stir frequently as to keep the chocolate from burning and/or seizing.
While it's melting, chop two of the Kit Kat bar packs into fine pieces. Because of the wafer inside, the pieces will be like crumbs.
Once the chocolate has melted, pour it over the cereal. Stir gently until all pieces are fairly coated with chocolate. Add in the Kit Kat crumbs and stir them around gently.
In a large gallon ziplock bag, pour in the chocolate cereal mix and the powdered sugar. Zip the bag up (with air inside) and shake the cereal until all pieces are coated with powdered sugar (some will be more coated than others, which is fine).
Chop up the other two Kit Kat bars in thicker, bite-sized pieces.
In a bowl, mix together the puppy chow and Kit Kats.
Enjoy!