In a bowl, combine chicken strips with soy sauce, black bean garlic sauce, and white pepper. Mix well and let sit for 15–20 minutes.
In a small bowl, mix soy sauce, dark soy sauce, black bean garlic sauce, and sugar. Stir well and set aside to allow the sugar to dissolve.
Thinly slice the onion, julienne the carrot, and chop the broccoli into small florets. Slice the chili pepper and mince the garlic.
Cook the egg noodles according to package instructions. Rinse under cold water to stop cooking and drain well.
Heat 1-2 tbsp of oil in a large wok or skillet over high heat. Add the marinated chicken and stir-fry until golden brown on all sides. Remove the chicken from the pan and set aside.
In the same pan, add another tbsp of oil. Stir-fry the onion and carrot for about 1–2 minutes until fragrant.
Add the garlic, chili pepper, and broccoli. Stir-fry for another 3–4 minutes. If needed, add 1–2 tbsp of water to help soften the broccoli.
Add the cooked noodles to the pan and stir-fry for 1–2 minutes so they absorb the flavors.
Return the chicken to the pan and pour in the prepared sauce. Toss everything together until evenly coated. Cook for another 1–2 minutes over medium heat, stirring constantly to ensure everything is well combined.
Serve hot, garnished with toasted sesame seeds, sliced green onions, or fresh cilantro if desired.