Cut off both ends of the cucumber and slice into 5mm thick rounds. Place in a bowl, add 1/2 tsp salt, massage, and let sit for 5 minutes. Rinse with water and drain.

Slice the chicken breast thinly and coat with potato starch.

Mix the seasoning ingredients (sugar, soy sauce, vinegar, gochujang, sesame oil, and sesame seeds) in a bowl. Add the cucumber and mix well.

Bring a pot of water to a boil, add the chicken, and simmer on low heat until the chicken changes color. Remove and drain the chicken, then add it to the cucumber mixture and mix.