Wash 1 pound of chicken thighs under cold water and pat them dry thoroughly with paper towels.

Slice the chicken thighs horizontally to make them thinner and ensure even cooking. Make several small cuts on the surface and lightly pound with the back of a knife to tenderize.

Season the chicken on both sides with kosher salt and ground black pepper.

Cut a 2-inch piece from the white part of a large green onion and thinly slice it. Also, thinly slice a small piece of onion.

Soak the sliced green onion and onion in cold water to remove their harshness. Set aside.

Thinly slice the green and red chili peppers for the sauce.

To make chili oil, heat cooking oil in a small pot and briefly stir-fry the red pepper flakes to infuse the oil with flavor.

Strain the hot chili oil into a mixing bowl.

To the chili oil, add soy sauce, vinegar, and sugar. Mix well until the sugar is fully dissolved.

Mince the garlic cloves and add them to the sauce.

Add water and sesame oil to the sauce and mix everything together.

Prepare the batter by mixing potato starch, a couple of pinches of salt, and a large egg in a bowl until smooth.

Coat each piece of chicken in the batter, ensuring it's lightly covered, and fry in oil preheated to 350°F (175°C) for about 5 minutes until golden.

Remove the chicken from the oil and let it drain. Reheat the oil for a minute and then double-fry the chicken for another 5-6 minutes until it's extra crispy and golden brown.

Remove the double-fried chicken from the oil and drain on a strainer.

Drain the soaked onion and green onion and rinse them under running water. Drain thoroughly.

Arrange a bed of lettuce leaves on a large serving platter.

Cut the crispy fried chicken into bite-sized pieces and arrange them on top of the lettuce.

Add the sliced chili peppers to the sauce, mix, and pour it evenly over the chicken.

Finally, top the dish with the drained green onion and onion mixture. Serve immediately.