Place chicken pieces in shallow baking dish. Pour 1 cup of marinade over the chicken. Massage the marinade into the chicken real well.
The next steps are from a korean chef’s site Seonkyong Longest(link here) Watch her video, it makes the steps easier to follow:
Heat frying oil 375°F in a thick bottom pot, such as dutch oven or cast iron wok/pot.
Whisk tempura powder, garlic powder, onion powder, curry powder, cornstarch and sugar in a large mixing bowl. Take the chicken out from the marinate, add into the dry ingredients mixture and toss evenly.
Slowly add water and mix. Start form ¼ cup and add 1 Tbsp per time as needed. We want the batter to be more thicker consistency than pancake batter.
Add the chicken pieces one by one into the hot oil carefully and fry for 6 to 7 minutes or until lightly golden brown and ¾ to “almost” fully cooked. Do 2 to 3 batches depending on the size of the frying pot. Remove from the oil and place on a cooling rack or paper towel lined baking sheet. Repeat with rest of the chicken.
When all the chickens are fried, increase oil temperature to 400°F for double frying. Carefully drop all the chicken and fry for 2 to 3 minutes or until golden brown and fully cooked. Remove form the oil and place on the cooling rack or paper towel lined baking sheet.
When the chicken comes out of the fryer, sprinkle a little bit of salt (not too much) over the chicken while it’s super hot, then brush the sauce evenly over the chicken. Don’t brush too much sauce, just a light coating...too much sauce might make it soggy
Serve hot.