Prepare the Sauce: In a medium bowl, whisk together dark soy sauce, chicken broth, rice vinegar, light brown sugar, sesame oil, sriracha, water, and black pepper until smooth. Set aside.

Marinate the Chicken: Toss the boneless chicken thighs with dark soy sauce and cornstarch until evenly coated. Let sit for about 10 minutes.

Cook the Chicken: Heat a skillet over medium heat, add cooking oil, then add marinated chicken, cooking for about 3 minutes on each side until golden brown. Remove and drain excess oil.

Sauté the Aromatics: In the same skillet, add minced garlic and ginger, stirring constantly for about 1 minute until fragrant. Do not burn.

Combine Components: Return cooked chicken to skillet with sliced red bell pepper and chopped green onions. Pour sauce over mixture, simmer for 3-4 minutes until sauce thickens.

Serve and Enjoy: Serve hot over steamed rice or as desired.