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

Combine the boneless chicken thighs with dark soy sauce and cornstarch in a separate bowl. Toss until evenly coated and let rest for at least 10 minutes.

Heat a large skillet over medium heat with a drizzle of oil. Add the marinated chicken in batches, cooking for 3 minutes per side until golden and crispy. Remove the chicken and leave about 1 tablespoon of oil in the pan.

Add minced garlic and ginger to the skillet, sautéing for about 1 minute until fragrant.

Return the chicken to the skillet, add the chopped red bell pepper and green onions, pour in the prepared sauce, and toss until well-coated. Let simmer for a couple minutes until the sauce thickens.

Serve over steamed white or brown rice.