Debone your chicken thighs.
Cut boneless skin-on chicken thighs into 2 inch pieces. I would split 1 chicken thigh into 3-4 pieces.
5 boneless skin-on chicken thighs
Add cut chicken into a bowl along with the remaining marinade ingredients. Let it marinate at least 15 minutes. The marinating step is optional but will end up more flavorful
5 boneless skin-on chicken thighs, 2 tsp salt, 1½ tbsp soy sauce, 1½ tbsp mirin, 1 tsp sugar, ¼ cup minced garlic, ¼ cup minced ginger, 1 tsp white pepper, ¼ cup corn starch, 1 large egg
In a large plastic bag, add enough corn starch to coat all the chicken. Add the chicken into the bag, seal, and shake until each piece is coated well.
1½ cups corn starch
Dust off excess corn starch from each piece of chicken and place them on a wire rack for 20-30 minutes. The chicken should hydrate the corn starch. Flipping the chicken after 15 minutes will help the process. IF you are low on time you can skip immediately to the frying process.
First fry at 300F - 325F for 4 minutes.
Turn up the heat to 375F and fry for another 1-2 minutes until crispy and golden.
Immediately season with salt and serve with kewpie mayo and a lemon wedge.