Cut 400g of pork shoulder into ¾in / 2cm cubes. Mix with ½ grated onion, 1 teaspoon of grated garlic, 1 teaspoon of grated ginger, ⅜ teaspoon of baking soda, 2 teaspoons of cornstarch, and 2 tablespoons of light soy sauce.
Marinate in the fridge for 18-24 hours. Toss with 5 tablespoons of cornstarch and leave until sticky, then coat in ½ cup of cornstarch.
For the sauce, mix ⅓ cup of sugar, ⅓ cup of apple cider vinegar, 3 tablespoons of pineapple juice, 3 tablespoons of ketchup, and ½ teaspoon of Worcestershire sauce.
Stir in 1 tablespoon of light soy sauce, 1 teaspoon of oyster sauce, 4 teaspoons of cornstarch, and ½ cup of water.
Heat 3 cups of vegetable oil in a wok to 350°F / 175°C. Fry the pork in batches for about 3 minutes, then drain.
Heat the oil to 390°F / 200°C. Fry the pork again in batches for about 1½ minutes, until deep golden and crisp.
Heat 1 tablespoon of vegetable oil in a clean wok. Stir-fry 1 minced garlic clove, 2 teaspoons of grated ginger, 1 chopped medium onion, ½ chopped red bell pepper, and ½ chopped green bell pepper.
Add the sauce and 1 cup of canned pineapple pieces. Simmer for 2 minutes, until thickened. Toss in the pork for about 10 seconds and serve immediately.
