I used chicken thighs and I removed the bone but left the skin. I double fried them to make it crispy outside but juicy inside.
I am sure there are many variations in zangi recipes since many izakayas in Hokkaido serve their version. To me, zangi is seasoned with sake and soy sauce but no mirin or sugar and the amount of soy sauce is more than tatsuta-age. Mine is seasoned enough to be eaten as is without dipping sauces.
Four chicken thighs: I removed the bone and visible fat but trimmed excess skin. I cut the thigh into small bite size pieces.
Marinade: Sake and soy sauce (about 1:1) with grated garlic and ginger (1/2 tsp each or whatever amount you like).
Potato starch (Katakuri-ko) for dredging.
Peanut oil for deep frying.
I added the chicken pieces and the marinade to a Ziploc bag, massage it to make sure all the pieces got coated and let it marinate in the refrigerator for (at least) several hours. I then strained the liquid over a colander and blotted the excess moisture using sheets of paper towel. I then dredged the chicken pieces in potato starch. I first deep fried in 320F peanut oil for several minutes turning frequently for a few minutes in two batches. I let it drain and rest for 3-5 minutes (the above). After skimming off any flour or debris in the oil, I turned the flame up a bit and waited for 5 minutes or until the temperature reached 350-360F, I re-fried the first batch for several more minutes until the surface darkened and became crispy. I repeated this for the second batch.
Although I have served similar dishes before such as kara-age and tatsuta-age, this one was somehow better. We really liked this "zangi" version of Japanese fried chicken. I admit I am a bit biased since I am from Hokkaido originally.