Marinade chicken: In a bowl, combine all the ingredients under the "Chicken Marinade" section. Cover and let marinade in the fridge for at least 3 hours.
Spicy pickled cucumbers: In a bowl, combine all the ingredients for the spicy pickled cucumbers and set aside to pickle.
Sesame slaw: toast your white sesame seeds and grind it with a mortar and pestle. Then add in the rest of the ingredients for the dressing, except for the shredded cabbage. Mix well and season to taste. Add in the cabbage and toss well to combine. Set aside
Dry breading: in a bowl, combine all the ingredients for the dry breading. Once the chicken thighs are marinated, remove the chicken thighs from the marinade and into the dry breading mixture. Coat the chicken thighs with the mixture well so that all the exterior is coated in the flour.
Frying: bring a pot of neutral/vegetable oil up to frying temperature (365-370F or 185-190C). Carefully drop in the coated chicken thighs and fry for 7-8 minute, flipping halfway or until golden brown on both sides. Remove from oil and let drain off of excess oil.
Gochujang sauce: Add all the ingredients into a pan and bring it to a simmer. Use the sauce to evenly coat each fried chicken thigh.
Assemble: Spread of the sesame dressing on top of the bottom bun, then followed with the coated fried chicken fillet, sesame slaw, spicy pickled cucumbers and lastly, the top bun.