Cut the chicken into 1 1/2-2 inch chunks. Combine soy sauce, sugar, minced garlic, sesame oil, ginger, salt, pepper, cornstarch, mochiko flour in a shallow platter or a sturdy plastic bag. Add the chicken pieces in there and squeeze them around to make sure everything is thoroughly combined and coating the chicken pieces. Cover with a cling wrap. If you use a bag, push all the air out and seal the bag. Lay the bag flat on a plate and put in the fridge to let it marinate for at least 8 hours. You can also put this in the freezer for up to 1 month. Simply thaw overnight in the fridge before using
When ready to cook:
Combine the mochiko flour, cornstarch, and salt as a dry coating for the chicken pieces
In a medium-size pot, add cooking oil to come up about 2 inches. Preheat over medium heat.
While the oil is preheating, coat each piece of chicken with the dry coating. Gently press the coating on the chicken pieces and shake off any excess.
When you stick a skewer into the oil, you'll see bubbles around it. The oil is sufficiently hot at this point
First frying:
Add a few pieces of the chicken at a time. Try not to crowd the pot and lower the temperature too much. Let them fry for 3-4 minutes (depending on the size of the chicken chunks) or until they are very lightly golden brown. Remove with a slotted spoon or skimmer and place them on an absorbent paper towel
Continue frying the rest in batches. Skim off any crumbs from the oil in between frying if necessary
Second frying:
The second frying will be quick. It is to crisp up the chicken. Make sure the oil is hot again
Starting from the first batch that you fry, add those pieces in there and let them fry for about 2 minutes or so. They will have a deeper golden brown this round. Starch coating usually doesn't brown as much compared to using all-purpose flour. They should be crisp
Keep warm:
Keep them warm on a cooling rack set on top of a baking tray to catch any dripping oil. I usually keep them warm in the oven.