Combine oyster sauce, sherry cooking wine, ground black pepper, and salt in a bowl. Mix well.

Add the thinly sliced chicken. Marinate for 10 minutes.

Heat 1 tablespoon cooking oil in a pan

Once the oil becomes hot, stir-fry the bell peppers for 1 minute. Remove from the pan and set aside.

Pour the remaining cooking oil on the same pan. Once the oil gets how, put the marinated chicken in the pan including the remaining marinade. Stir fry for 5 minutes or until the chicken turns light to medium brown.

Add the cooked bell peppers. Continue to stir-fry for a few seconds.

Combine the chicken stock and cornstarch. Mix well and then pour into the pan. Stir-fry until the texture of the sauce thickens.

Transfer to a serving plate.