You want to cut the beef in strips against the grain.
In a large bowl, add the beef strips, 2 teaspoons of cornflour, 1 tablespoon of soy sauce, 2 teaspoons of sugar, and the Shao Xing wine. Mix well and leave for a minimum 10 minutes.
When ready to stir fry the ingredients, get a large wok or deep non-stick pan. Heat 1 tablespoon of oil on a high heat. Add the beef and marinade and quickly stir fry until the beef starts to cook - around 2 minutes.
Remove the beef and put it to one side.
Heat the remaining oil in the wok, then add the garlic and ginger and stir fry for 20 seconds. Then add the black bean and bell peppers. Stir fry for another 30-40 seconds. You want the bell peppers to still retain their shape and crunch.
Add the beef to the wok, then the oyster sauce, remaining soy sauce and water. Give everything a good stir.
Turn the heat to a medium and let simmer for 3 minutes, giving it a stir occasionally.
Once the sauce has thickened slightly, it's ready to serve. My mum's version uses slightly more ginger and she adds a splash of sesame oil at the end for fragrance. I've simplified it over the years for a weeknight dinner, but the core of the recipe - the fermented black beans, the velveted beef, the crisp peppers - is exactly how she taught me.
Serve this with rice or over noodles.