In a bowl, cover 20g black beans with 100ml hot water. Mix briefly, stand for 2-3 minutes, rinse & drain. Add the chopped garlic, 1 tsp of vegetable oil, sugar & sesame oil. Roughly mash, mix well & set aside.
Add the remaining 2 tsps vegetable oil to a hot wok over medium heat. Add the chopped peppers & onion. Stir-fry for 1 minute. Add the prepared black bean mix and stir-fry for a further 1-2 minutes until aromatic.
Add the salt, msg, white pepper, dark soy sauce & water. Mix well, increase the heat to high and stir-fry for 2-3 minutes.
Add the oyster sauce. Stir-fry for 1 minute until the sauce begins to thicken slightly. Thicken further with the potato flour / corn flour mix and stir-fry for a further 30 seconds until the sauce reaches the desired consistency. Finish with 1-2 tbsps rice wine.