Begin by preparing your sauce. In a small mixing bowl, combine soy sauce, brown sugar, rice wine vinegar, sambal oelek, garlic, and sesame oil. Stir well to combine and set to the side.
Cut chicken thighs into bite sized pieces. Place in a medium sized bowl and cover with ⅓ cup of the prepared sauce mixture. Allow chicken to marinate for at least 30 minutes and up to 24 hours.
Once the chicken is marinated, beat one egg and pour over top of chicken. Mix well to coat.
In a separate bowl, combine ingredients for crispy coating, including flour, cornstarch, baking powder, paprika, garlic powder, salt, and pepper.
Coat chicken pieces in flour mixture, it will be very sticky.
In a deep skillet, add ½ inch of cooking oil over medium high heat. Once oil is hot, begin adding chicken, working in batches. Flip pieces occasionally to ensure even cooking. The chicken is done when it is golden brown all around.
Once cooked, transfer chicken pieces to a paper towel lined plate to drain off excess oil.
Pour remaining teriyaki sauce in a small saucepan over low heat and allow to thicken slightly. Pour sauce over cooked chicken and enjoy.