In a small bowl, combine the hoisin sauce, soy sauce, sugar, sesame oil, 1 tablespoon of the rice vinegar. In a separate bowl dilute the corn starch in ¼ cup of the chicken stock and mix with the hoisin sauce mixture. Set aside.
Mix the remaining rice vinegar with the chicken, season with salt and pepper and let it marinate for about 15 minutes.
In a large wok set on high flame, heat the wok to smoking point then add 1 tablespoon of the vegetable oil, take a teaspoon of the ginger and drop in the hot oil and quickly stir fry for 2 seconds, add the vegetables to the wok, stir fry continuously stirring fry for few minutes; using a slotted spoon remove onto a platter, add 1 one teaspoon of the oil to the hot wok and stir fry the cashews for a minute or two then remove onto the platter with the vegetables. Return the wok to the stove and reheat until in starts to smoke, add the remaining oil and swirl the oil in the wok to coat the surface, add the garlic and the rest of the ginger and the pepper flakes, cook stirring for 1 minute, add the chicken pieces and stir fry until browned, add the ¼ cup of the chicken stock and cook covered on high heat for a few minutes longer, until the chicken in no longer pink and thoroughly cooked. Return the vegetable to the wok and stir to incorporate with the chicken, pour the sauce on top and stir to coat, let it come to a boil and cook until the sauce thickens (this process should take only 2 to 3 minutes). Serve warm with Hot steamed fluffy rice.