Thinly slice green onions and set aside. Cut chicken into 1-inch pieces. Combine chicken, salt, cornstarch, and water in a medium bowl; then, set mixture aside.
Peel and finely grate ginger using a hand-held rasp-style grater or box grater; transfer ginger to a small mixing bowl. Grate or mince garlic. Add it to the ginger with the gochujang, mirin, honey, sesame oil, and vinegar, and stir until well-combined. Set sauce aside.
Heat a large, heavy-bottomed frying pan over medium-high heat. Once hot, add oil, swirling to coat bottom. Add chicken and spread pieces into a single layer. Cook until well-browned on underside, 2-3 minutes. Turn pieces over and cook until browned on second side, 2-3 minutes. Transfer chicken to a bowl.
Reduce heat to medium-low and add sauce mixture to pan. Cook, stirring constantly, until hot, about 30 seconds. Return chicken to pan and toss until well coated.
Transfer chicken to a serving plate. Sprinkle with sesame seeds and reserved green onions, and serve immediately.
Ingredients
2 green onions 1 1/2 pounds boneless, skinless chicken thighs 1 teaspoon salt 4 teaspoons cornstarch 1 teaspoon water 1/2 inch fresh ginger (1/2 inch is 1 Tbsp. minced) 2 cloves garlic 3 tablespoons gochujang (sweet and spicy Korean red pepper paste; buy at grocery stores, Asian markets, and online) 2 tablespoons mirin 1 tablespoon honey 1 tablespoon toasted sesame oil 1 tablespoon seasoned rice vinegar 2 tablespoons vegetable oil 1 teaspoon toasted sesame seeds