In a separate bowl, combine 1/2 cup of all – purpose flour, 1/2 cup of cornstarch, 1 egg, 1/2 cup of water, and a pinch of salt. Stir well until a smooth batter forms. The consistency should be thick enough to coat the pork evenly.​

Dip each pork strip into the batter, ensuring it’s fully coated.​

Heat about 2 inches of oil in a deep pan or wok over medium – high heat. When the oil reaches 160 – 170°C (you can test by dropping a small bit of batter; it should sizzle and float), carefully add the coated pork strips to the oil. Fry in batches to avoid overcrowding. Fry for 3 – 4 minutes until the pork turns light golden – brown. Remove the pork with a slotted spoon and place it on a plate lined with kitchen paper to drain excess oil.​

Increase the heat to high and re – fry the pork strips for 1 – 2 minutes until they turn a deep golden – brown and become extra crispy. Remove and drain again.​

In a bowl, whisk together 2 tablespoons of ketchup, 2 tablespoons of rice vinegar, 1 tablespoon of sugar, 1 tablespoon of light soy sauce, 1/2 teaspoon of salt, and 1/2 cup of water.​

Add 1 tablespoon of cornstarch to the sauce mixture and stir until well – combined.​

Pour out most of the oil from the wok, leaving about 1 tablespoon. Heat the remaining oil over medium heat.​

Add the onion chunks to the wok and stir – fry for 1 minute until they start to become translucent.​

Add the green and red bell pepper chunks and continue to stir – fry for another 1 – 2 minutes until they are slightly softened.​

Pour the prepared sweet and sour sauce into the wok. Stir constantly until the sauce thickens and starts to bubble.​

Add the fried pork strips to the wok. Toss the pork in the sauce to ensure it’s evenly coated.​