In a bowl, marinate the diced chicken with soy sauce, oyster sauce, and sesame oil. Let it sit for 15-20 minutes.

In a wok or large skillet, heat some cooking oil over medium-high heat. Add the marinated chicken and stir-fry until cooked through. Remove from the wok and set aside.

In the same wok, add a bit more oil if needed and stir-fry the walnuts until lightly toasted. Remove and set aside.

Add a bit more oil to the wok and sauté the garlic, onion, and bell peppers until slightly softened.

Return the cooked chicken to the wok and mix well with the vegetables.

Add hoisin sauce to the wok and stir everything together until well combined.

Finally, add the toasted walnuts and stir to incorporate.

Season with salt and pepper to taste.

Garnish with chopped green onions and sesame seeds before serving.

Serve hot over steamed rice or noodles.

Enjoy!