Add the water and cornstarch to a jar or a medium bowl. Stir well to dissolve the cornstarch. Next, add in the soy sauce, chicken broth, brown sugar, hoisin sauce, rice vinegar, sesame oil, ginger powder, minced garlic and crushed red pepper (if using). Stir with a fork or small whisk until combined.
Cover the sauce and place it in the refrigerator if you are not using it right away. Stir it right before using because the cornstarch tends to settle at the bottom.
Season the chicken on both sides with the salt and black pepper.
Heat the oil over medium high heat. When the oil is hot, but not quite smoking, add the chicken.
Cook for 4 – 5 minutes until browned. If you’re not using a non-stick skillet then wait for the chicken to release before turning so that it doesn’t tear.
Turn each piece and cook for 4 – 5 minutes to brown on both sides.
Lower the heat to medium and add the sauce, stir and turn the chicken to coat on both sides.
When the sauce comes to a simmer lower the heat to medium-low, cover and cook the chicken thighs with the sauce for 6-8 minutes or until the chicken is cooked through. Keep the sauce at a simmer, if it is boiling too vigorously lower the heat a bit. Turn the chicken a few times during the cooking time. The sauce contains sugar, and we don’t want it to burn.
Use an instant read thermometer to make sure the internal temperature reaches at least 165°F on the thickest part of the largest piece. If it is not up to temperature continue cooking a few more minutes and check again.
Serve the sticky chicken thighs with rice, noodles, vegetables or your favorite side dish.