Preheat the sunflower oil for cooking. Ensure that you heat enough for deep frying the chicken.
Mix the chicken with the cornflour and add to the preheated hot oil and cook for 5 to 8 minutes or until chicken is no longer pink in the centre and the outside is brown and crispy. Remove the chicken from oil and blot with kitchen paper to remove excess oil. Set aside.
Add 1 tablespoon of the oil you used to cook the chicken to a separate pan. Add the garlic, coriander and chilli (if using). Cook and stir for a few minutes until fragrant then add the rest of the ingredients for 2 minutes or until hot. Add chicken and mix through. Remove from the heat and serve hot.