Soak the potatoes in a bowl of cold water until ready to use.
Fill a bowl with 2 cups (16 fl oz/ 500 ml) water and add the eggplant (aubergine) and 1 teaspoon salt. Soak for 15 minutes.
Heat the oil in a wok or deep saucepan to 300°F/150°C, or until a cube of bread browns in 1 1/2 minutes. Add the green bell peppers and deep-fry for about 15 seconds. Use a slotted spoon to carefully remove the peppers from the oil and drain on paper towels.
Drain and pat the potatoes dry with paper towels. Add to the oil and deep-fry for about 4 minutes until golden brown. Use a slotted spoon to carefully transfer the potatoes to a plate lined with paper towels.
Drain and pat the eggplants dry with paper towels. Heat the oil to about 350°F/180°C, or until a cube of bread browns in 30 seconds, add the eggplants, and deep-fry for 2 minutes. Use a slotted spoon to carefully transfer the eggplants to a plate lined with paper towels.
Combine the soy sauce, sugar, remaining 1/2 teaspoon salt, and cornstarch (cornflour) in a bowl and mix into a sauce. Set aside.
Pour out most of the oil, leaving about 1 tablespoon in the wok over medium-high heat. Add the ginger and garlic and stir-fry for 1–2 minutes until fragrant. Add the potatoes, eggplants, and green peppers, increase to high heat, and stir-fry for 1 minute.
Add the wine and sauce to the wok. Bring to a boil, stirring, for 30 seconds to thicken the sauce. Transfer to a serving plate and serve with rice.
Adapted from China: The Cookbook by Kei Lum and Diora Fong Chan (Phaidon, 2016)