How do I make Chicken 65 crunchy?

My older sister keeps telling me that the Chicken 65 she had at a restaurant had this crunchy taste and since I’ve made this recipe twice now: I’ve been unable to get that crunch. I believed that it was an issue with the flour I was using, but that doesn’t seem to be the case? My first Chicken 65 recipe consisted of just using Corn Starch–at the time there was no Corn Flour available: the chicken after being deep-fried came out soft but not crunchy. On the second try, this time with Corn Flour mixed with Rice Flour and a tablespoon of Corn Starch: there still remains to be no crunch, only a soft coating. What ingredient am I missing to get that crunch?