Let's prepare the sweet vinegar sauce. Shred the dashi kombu seaweed with a pair of kitchen shears. The shredded pieces are easier to make dashi stock and are also edible.
Snap the red chili pepper in half, remove the seeds and cut into rings.
Pour the water in a small pot. Put in the kombu seaweed, vinegar, soy sauce, sugar and salt.
Turn on the burner, stir and bring it to a boil.
When it starts to boil, turn off the burner and pour the sauce in a large bowl.
Drop in the red chili pepper.
Let's cut the vegetables. Remove the root end of the onion and slice into 7~8 mm (0.3") slices along the grain.
Separate the onion layers.
Slice the carrot into 5~6 mm (0.2") pieces along the grain and chop them into strips.
Slice the bell peppers into rings. Avoid using the seed-containing part to make the dish more presentable.
Heat the oil in a pan and stir-fry the onion and carrot for one and a half minute.
When they are slightly softened, turn off the burner.
And drop the vegetables in the sweet vinegar sauce.
Add the bell peppers and submerge the vegetables in the vinegar sauce with a pair of kitchen chopsticks.
Let's prepare the chicken thigh. Make cuts in tough stringy parts with the tip of a knife.
Cut the chicken thigh in half and divide each half into 4 pieces.
Put the meat in a bowl and add the soy sauce and sake.
Grate the ginger root.
Squeeze the grated ginger and pour the ginger juice over the meat.
Gently rub the chicken with the seasoning until the excess liquid is absorbed.
Let the meat sit for 10 minutes to marinade.
Now, arrange the chicken pieces on a tray covered with a paper towel.
Cover it with another paper towel and gently press the meat to remove the excess liquid.
Put the potato starch in a plastic bag.
Add half of the chicken pieces to the bag and shake to coat.
Then, add the rest of the chicken in the bag and shake to coat thoroughly.
This will help to coat the chicken quickly and evenly.
Place the chicken on a tray.
Heat the oil to 170 °C (340 °F) and place the chicken into the oil from large pieces. Check the small bubbles and the sizzling sound to get the right oil temperature.
Don't touch the meat right after placing it in the oil. Let the chicken sit for a few seconds.
When the surface starts to become crispy, flip the pieces over.
Deep-fry them for about 5 minutes while occasionally turning the chicken over.
When the surface becomes golden brown, place them onto a cooling rack covered with a paper towel to remove the excess oil.
When they are still hot, place the chicken in the bowl of the sweet vinegar sauce.
Roughly mix them from the bottom to coat them with the sauce. We enjoy the crispy texture of the chicken so we don't soak them in the sauce for a long time but you can adjust the dipping time to taste.
Serve the chicken and vegetables on a plate along with a butterhead lettuce leaf. Pour over the remaining sauce.
Finally, sprinkle on the toasted white sesame seeds.
As shown in this recipe, 1.5 to 2 cm (0.2"~0.8") depth of frying oil should be enough to deep-fry the chicken with a pan.
If this dish is too sour and too spicy for you, you can reduce the amount of vinegar and chili pepper.