In a mixing bowl, combine sliced boneless chicken thighs with egg white, cornstarch, salt, and black pepper. Let marinate for 10-15 minutes at room temperature.

Heat vegetable oil in a large skillet over medium-high heat. Carefully add the marinated chicken in small batches and fry for 4-6 minutes until golden brown and crispy.

In the same skillet, lower the heat and pour in sesame oil. Sauté minced garlic, ginger, and dried red chilies for 1-2 minutes until fragrant.

Add ketchup, soy sauce, chili garlic sauce, vinegar, and sugar, mixing well. Let simmer for 2-3 minutes, adding water if necessary.

Toss the crispy fried chicken into the sauce, gently stir to coat. Simmer together for 1 minute.

Remove from heat and transfer to a serving dish. Garnish with sliced green onions and toasted sesame seeds.