Cut the meat into approx. 1 cm thick slices and the basil into approx. 1 cm wide strips.
Fry the chicken fillet pieces in a little oil until they are through, then add the basil, coriander, oyster sauce, sugar and optionally a little salt, continue to fry briefly and then remove from the pan.
Put some oil in the same pan and fry the onion with the chillies in it until the onion becomes soft. Add the meat again, heat it up briefly, add the coconut milk and let it simmer a little.