Combine the oyster sauce, soy sauce, fish sauce and sugar together in a bowl.

In a wok or a skillet, heat the oil over medium heat. Add the onions and saute until soft and translucent, about 5 minutes. To help the onions cook faster you can add a splash of water and close the lid to allow it to steam for a minute. Then uncover and cook until all the water has evaporated.

Once the onions are soft and translucent, add the garlic and Thai chilies and stir until the garlic starts to brown.

Add about ¾ cup (180 ml) of the stock, the sauce mixture, and ground black or white pepper then stir to mix. If you want to darken the colour, add a dash of black/dark soy sauce.

Add the bell pepper and cook for about a minute, then turn off the heat and stir in the basil just until wilted. Taste the sauce, and if it is too salty, add the remaining stock or water to dilute; however, it should taste slightly too salty at this point because you will be adding protein to it.

Use right away, or allow to cool and keep in the fridge for at least a week. When ready to use, reheat the sauce and pour over pan seared protein such as fish, thinly sliced steak or pork chops - or use it as a stir fry sauce! Watch the video for a demo of how to use the sauce!