Cut each chicken thigh into 2 to 3 smaller pieces. Place them in a large bowl, and stir in the soy sauce, black pepper, and bouillon powder. Cover and refrigerate for a couple of hours, or even overnight.
When ready to cook, let the chicken come to room temperature on the counter for 20 minutes. Heat the oil in a saucepan over medium-high heat, and add the ginger, garlic, and bird’s eye chili. Sauté for a minute, until fragrant, then add the green pepper and chicken. Fry for 2 to 3 minutes, coating the chicken in the ginger, garlic, and chili mixture.
Turn down the heat to low, and cook gently for 10 to 15 minutes, covered, until the chicken is cooked. If the pan looks like it’s drying out, add 1/4 cup of water.
Whisk the vinegar, cornstarch, and sugar in a small bowl. Once the chicken is almost cooked, uncover the pan, and add the vinegar-cornstarch mixture. Continue to cook for a few more minutes, until the sauce thickens slightly. Taste and add salt to taste.
Serve, garnished with green onions and cilantro, over rice or noodles. This dish reheats and freezes very well; the dish is even better on the second day. Leftovers will keep refrigerated for 1 week or frozen for up to 3 months.