Make a Batter using Flour and Corn Starch. For every 1 part corn starch, put in 4 parts flour. Then slowly add lukewarm water and mix until it makes a pancake batter like consistency. (Not too sticky not to runny- don't use hot water for it will cook the flour, and not cold water for it will be harder to mix)
Dip/coat each onion ring in the batter
On a separate bowl, prepare pure corn starch. Coat Battered Onions with starch one by one
After coating with starch, dip again in Flour batter
Lastly, coat rings with bread crumbs until fully covered and deep fry.