Steps

1. Prepare a large single piece of chicken thigh weighing over 350g (preferably over 400g). [This is the key!] Using a skin-on single piece enhances the effect of trapping the meat juices.
   🕒 02:00
2. On the flesh side of the chicken thigh, poke numerous holes with a fork without piercing the skin. [This is the key!] Poking holes allows the seasoning to penetrate quickly and helps the meat absorb the moisture from the egg added later.
   🕒 02:10
3. Cut the chicken thigh in half lengthwise, then cut each half into 3 pieces for a total of 6 pieces. [This is the key!] Cutting them larger than usual prevents the meat's moisture from escaping during frying, resulting in a juicy finish. Be careful not to peel off the skin.
   🕒 02:31
4. Add the cut chicken thigh and 1 egg to a bowl, gently knead without peeling the chicken skin, and allow the meat to absorb the egg moisture. [This is the key!] The moisture from the egg entering the meat creates a moist and juicy texture.
   🕒 03:17
5. Once the chicken thigh has absorbed a sufficient amount of egg moisture, add 2 tbsp soy sauce, 1 tbsp cooking sake, 1/2 tbsp sugar, 1/2 tbsp oyster sauce, 1-2 cloves garlic (grated), and black pepper, to taste (generous amount). Gently knead without peeling the chicken skin. [This is the key!] Sugar has water-retaining properties and helps to lock in the meat's moisture. Oyster sauce adds depth and richness.
   🕒 03:51
6. After kneading for a while, add 2 tbsp potato starch and coat the entire chicken thigh.
   🕒 04:44
7. Once the potato starch is incorporated, add 1/2 tbsp sesame oil and knead to coat the entire chicken thigh. [This is the key!] Coating with egg, then potato starch, and finally sesame oil creates a film on the meat, trapping the meat juices.
   🕒 04:51
8. Cover with plastic wrap, pressing it directly onto the surface, and marinate in the refrigerator for 30 minutes to 1 hour. [This is the key!] Marinating for too long can cause the meat's umami and moisture to leach out due to the salt, so strictly adhere to the marinating time.
   🕒 05:20
9. Just before frying, pour vegetable oil into the pot to a depth of about 2cm and heat to 170℃. [This is the key!] If you coat the chicken before the oil is properly heated, the coating will dissolve, and it won't be crispy. A good indicator of 170℃ is when inserting chopsticks causes continuous bubbles to rise.
   🕒 06:04
10. Thoroughly wipe off any excess marinade from the marinated chicken thigh.
    🕒 06:43
11. Coat the chicken thigh with potato starch, to taste, then roll it up with the skin side facing outwards to shape it. [This is the key!] Rolling it up wrapped in the skin maximizes the trapping of meat juices and moisture.
    🕒 06:54
12. Once the oil reaches 170℃, carefully place the chicken into the pot with the rolled seam facing down to fry. [This is the key!] Frying with the rolled seam down helps to fix its shape. For the first 1-2 minutes of frying, do not touch it to prevent the coating from coming off.
    🕒 07:28
13. After about 2 minutes, flip the chicken thigh and fry gently, being careful not to burn it, until the entire piece is a nice golden brown color.
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14. Once the coating starts to color, periodically expose the karaage to the air while frying. [This is the key!] Exposing it to the air allows excess moisture from the coating to evaporate, resulting in a crispy finish.
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15. When the coating is a nice golden brown color, remove from the oil and drain thoroughly.
    🕒 08:35
16. Arrange on a plate and serve with lemon, if desired.
    🕒 08:49