Crush garlic with cilantro and coriander in a mortar and pestle to create a paste.

In a small bowl, combine oyster sauce and fish sauce.

Add the garlic-cilantro-coriander paste to the sauce mixture.

Mix in sugar and ground pepper until well combined.

Slice the pork into thin, 2-inch square pieces.

Place the pork into the marinade.

Refrigerate and let it marinate for at least 1 hour, or longer for better flavor.

Remove the pork from the marinade.

Skewer the pork onto bamboo (soaked in water) or metal skewers.

Grill over medium heat, turning occasionally, until the pork is nicely browned and the juices run clear.

Alternatively, broil the pork in the oven until nicely browned and juices run clear.