- Marinate the pork: Cut the thinly sliced pork belly into 1.5-inch wide bite-sized strips. Add to a medium-sized bowl, followed by the ground white pepper, low sodium light soy sauce, Shao Xing rice wine, potato starch and sesame oil. Mix to coat, then set aside.
- Make the sauce: Mix together the potato starch, white sugar, XO sauce, low sodium light soy sauce, Shao Xing rice wine, oyster sauce, fish sauce, Chinkiang vinegar, sesame oil and pure chili oil (if using) in a small measuring cup or bowl until combined well.
- Prepare the fresh ingredients: Smash the garlic with the flat side of your knife, then roughly chop. Thinly slice the yellow onion, cut the spring onion into 1.5-inch pieces (separate the white and light green parts from the dark green parts), mince the ginger, chop the fresh Bird’s Eye red chilies. Thinly slice the large red chilies at an angle (deseed if desired). Separate the stem and leaves of the water spinach. Cut the stems into 3-4cm pieces. Rinse both the stems and leaves in separate colanders and set aside.
For the XO Sauce Pork and Water Spinach Stir-fry:
- Cook the pork: Heat 1 tablespoon canola oil in a large wok (or deep heavy bottomed frying pan) over high heat. Once hot, add the pork and immediately spread the pieces out in the wok. Allow to sear for 30 seconds, then stir-fry for 1 minute until mostly no longer pink and almost cooked through. Use a slotted spoon to transfer to a clean bowl and set aside. If the pork was very fatty and released a lot of grease, discard all but 2 tablespoons of the rendered fat/oil from the wok. If not and more oil is needed, add oil until there is 2 tablespoons of oil/fat in the wok.
- Stir-fry the onion and aromatics: Heat the rendered fat and oil in the wok over medium-high heat. Once hot, add the yellow onion and spring onion white and light green parts. Stir-fry for 30 seconds until translucent. Add the garlic, ginger, both types of red chilies and stir-fry for 30 seconds until fragrant.
- Add the water spinach stems: Add the stem parts of the water spinach and stir-fry for a minute until they start to soften.
- Add the pork and water spinach leaves: Add the pork, water spinach leaves and kosher salt. Pour half cup of water around the rim of the wok. Cover for 1 minute to help the leaves soften. Uncover and toss everything until evenly combined.
- Pour in the sauce: Give the sauce a quick stir with a spoon to loosen the potato starch that will have settled at the bottom. Pour it over everything and stir-fry for 1 minute until everything is combined well and the sauce starts to thicken.
- Stir through spring onion: Stir through the spring onion dark green parts and switch off the heat.
- To Serve: Transfer to a serving plate or dish and serve immediately with warm steamed rice.