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 and well combined.

Toss the boneless chicken thighs with dark soy sauce and cornstarch in a large bowl. Let the chicken rest for about 10 minutes.

Heat a tablespoon of oil in a large skillet over medium heat. Add the marinated chicken thighs in batches and cook for approximately 3 minutes on each side.

Using the same skillet, add minced garlic and ginger, stirring quickly for about 1 minute or until fragrant.

Return the chicken to the skillet, add chopped red bell pepper and green onions, pour the prepared sauce over the mixture, and toss to coat.

Allow the dish to simmer for about 2 minutes until the sauce thickens slightly, then remove from heat and serve hot.