Mix the garlic, oyster sauce, soya sauce, salt and cornflour in a bowl. Add the chicken slices and mix well to ensure the chicken is well coated. Refrigerate for 2 hours.
In a large wok, stir fry each of the vegetables (except the bean sprouts) separately in a little hot olive oil for about 2 minutes each, then keep aside in a bowl, Similarly fry the bean sprouts but only for 1 minute. Add to the bowl.
Remove the chicken from the marinade and stir fry in a little hot olive oil until cooked (around 3 to 4 minutes.
Return all the vegetables to the wok and mix well.
Combine the oyster sauce, cornflour and chicken stock in a jug and then add to the wok. Season and bring to a simmer. Serve immediately.